This is a general guide to getting the Achievements for Exploration (completing delves/solo dungeons by beating bosses), completing quests and getting around to get Skyshards, Lorebooks, Dolmens and the like.
I'm not actually going to post spoilers which say where these things are, just post the various tips and tricks that you'd never know having adventured outside of Cyrodiil. So, for instance, if you want to find a map of Skyshards or want to use an add-on, or would rather just stumble upon them based on the actual hint in your Journal is immaterial to this guide.
General Travel Advice (how to get around Cyrodiil)
* Getting to Cyrodiil is easy. Just hit your L key to go to the Alliance War screen, click the Campaign tab and choose one. If you want a Campaign that's totally dominated by your Alliance for ease of getting around, check this site:
http://esostats.com/
* The second most important tip is to make sure that in your Settings > Game Settings that you have "see enemy faction" enabled, so that the little badge floating above their heads is visible, which makes nearby players that aren't stealthed stick out like a sore thumb. The enemy is the color that your Alliance is not, so in case you're AD you need to watch out for Red and Blue, but it will be hard to see from as yellow makes you run directly into things in large groups without any sense of caution, which is a known bugs and will eventually be fixed in an upcoming genome patch through natural selection. I kid.
* When traveling around, you can go into Keeps (the big castle icons on the map) and use the Transit Shrines (NOT wayshrines) which have wizards standing around them to teleport around.
* You can go TO anyplace your Alliance currently controls that's connected to the Transit lines which are
highlighted. There's lines connecting places on the map that your Alliance currently controls but do not control intervening locales which are not highlighted, and you can't use the transit shrines to get to them, you have to pick the closest accessible place and then hoof it. This will be easy to figure out as clicking on the Alliance-controlled but "unconnected" locales won't let you travel there.
* Unlike how Wayshrines work, when you use a Transit Shrine and you're looking at the map, when you click on a place you just immediately go there. There's no "are you sure" message.
* A side note: To get out of Cyrodiil, go to one of the two places in your Alliances corner of the map via Transit Shrines and then just run over to the Wayshrine and that'll let you get back to the rest of Tamriel. Also, if you get stuck and no other means of egress works you can simply hit L for the Alliance War screen and then choose a different campaign to Guest in, go there, and use the Wayshrine or what have you there. This is not at all obvious!
* If you plan on spending much time in Cyrodiil don't be a cheapskate and buy the 48k gold light horse and start feeding it apples every day. This will save you 10 trillion hours of travel time running around Cyrodiil. Also, spend a little time PvPing and get the Rapid Maneuver skill which makes both running and riding your horse faster. In fact, uniquely so far as I know, hitting the hotkey for this ability while mounted you immediately unmounts you and you then cast the spell, then can hit H to remount and enjoy the speed burst. I do this repeatedly everywhere I go now.
* Some places are meant to have choke points between them, in particular Gates which look like Roman triumphal arches on the map. When near them (especially when anywhere near the Elder Scroll temples which, on the map, look like pavilions) stick to the roads (check the route on your map first) as you will waste an incredible amount of time trying to get over and around impassible walls and mountains otherwise. If near a gate, go through that gate. There's plenty of other places where you can just run/ride straight through, however you may want to keep a bit of an eye out for precipitous drops, as the landscape is much, much more open and "not on rails" (one might even say Elder Scrolls-ish) than other zones, but that also means that at full gallop you might just run off a cliff. This is annoying mostly because that's where dungeons and overland camps full of rather non-dangerous mobs are, but it never pays to take 80% falling damage right as you aggro an entire critter camp.
* Speaking of critters and falling damage, when you die (and you will) dying to the aforementioned causes allows you to resurrect right where you are. Whereas dying to other players for the most part requires you resurrect at an Alliance-controlled locale (highlighted lines, remember) or a Forward Camp (a player-placed PvP item which, fair warning to tourists, is likely near a siege or a big fight. The most important thing to bear in mind is that these things are highly subject to change and a Forward Camp (FC in the parlance, and they look like tent icons on the map) wears out after a certain number of uses, and a Keep or the like can definitely be taken in 8 minutes or less so plan accordingly. The main punishment in Cyrodiil is being forced to run back somewhere, so do not dismiss my notes about horses above.`
* If you're a'scared of PvP battles, what you need to know is that Cyrodiil's population is incredibly sparse and you can easily spend hours without seeing anyone else when you're out looking for PvE goals, as the PvPers are all running from Keep to Keep for the most part.
* That being said, the true terror of Cyrodiil is NPC guards of the enemy Alliances. Stay a decent distance away from enemy Alliance locales on your map. They can spot you while Stealthed, and they will chase you for a decent interval, and they call their friends and their spellcasters hit like howitzers.
* And yet, sometimes you must make it through an enemy Gate. In particular, each Alliance will have a couple skyshards deep behind their Gates even in campaigns where one Alliance dominates as there are some locales that cannot be taken by other Alliances. The main way to get through this is to get as close as you can to the NPC defenders' aggro range (learn this from experience if you must, just run like hell away from them until you know where their aggo boundary is. Then mount up, get on your horse and run through, making sure your horse is at full stamina so you don't immediately get knocked off. Once you get knocked off, run at a full sprint away, using heal abilities or potions and eventually they'll give up. Once they see you you will not be able to use stealth for about 30 seconds after you escape. Don't even bother using invisibility as they will simply laugh and blast you.
Once through, you're not especially more likely to run into enemy PvPers as, just like in the rest of Tamriel, most people teleport everywhere and hang around indoors, not just milling about outside the walls. There is a chance that there'll be an especially patient ganker or two at a Skyshard, but this is actually less likely the more territory the enemy controls.
* Warning: slaughterfish live in some water in Cyrodiil, in particular around the Imperial City in the center of the map. Also, the lake around there has terrain the is freaking annoying to climb back up out of in some places, and some notorious places where jumping around will get you stuck. Just be careful.
* All levels, from 10 to VR 12, are "scaled" to be closer in power to one another in Cyrodiil. This means two things: First, the mobs are not terribly dangerous, despite all ostensibly being VR 5. Secondly, that means that the level differences between players isn't so extreme, but if you're not VR level and you see a VR level enemy, they will in all likelihood make quick work of you. If it's a Sorcerer they will throw a sissy purple crystal at you, you will fall down and never get up (unless you're l33t, in which case they'll ride the lightning to safety and say they killed over tea back home, where as if they win they stand over you in the traditional "my what a lovely tea party" bon voyage of the victor. If it's a Dragonknight they will laugh while you ineffectually attempt to damage them and, after 20 seconds or so, will root you with Talons (double-click 8 times to get out of all 4 spammed) then hit their "I win" button and deploy a PvPride Flag and laugh as you die like the chivalrous knight of yore - try to take it with good grace, as it will not be the last time, unless you catch them IRL at the local RenFest, where you can kick their ass til their Mom intercedes. Nightblades could kill you from stealth before you react, but will really just stay stealthed in fear that you have a DK or Sorc with you and creep away to scan the forum for any news that Shadow has been fixed. Templars are the easiest to disarm - just /w them that you're impressed that they managed to get to VR level as a Sword and Board gimp and that they totally deserve a boost to their powers and they'll follow you around healing you and their vanity pet until the lovely gold of their nimbus attracts one of the aforementioned other classes who will rapidly de-heal you and your new friend.
* Big red circles on the ground are very bad, like a Mr. Yuck sticker, and are meant to notify you to run away run away.
* Pets do not stealth. You can be in stealth and unless someone practically walks on top of you will never see you unless you do something crazy like switch weapons or walk within 200 yards of an enemy Alliance NPC. You are literally invisible when stealthed - but so are they. Magelight can prevent sneak attacks from stealth, but it's also a wonderfully attention-grabbing beacon when you're not in stealth.
* Do NOT ask questions in Zone chat as it is meant solely for LFG and/or making the less-vocal minority of fully-functioning mature human beings experience a deep and abiding shame in their species. Repeat: DO NOT ask questions there, just come here and read this guide if you forget something or PM me. If you post here on the PvP forums you may be sucked into an inescapable morass of a ***-for-tat, sophomoric foofaraw which locks you into an inescapable loop you cannot simply /stuck to escape and worse than any infinite loading screen.
Delves/Solo Dungeons (how to get find Boss mobs for Achievements)
Here's my previous guide to the Imperial Cave Delver Achievement:
My guide to getting the Imperial Cave Delver achievement in Cyrodiil, i.e. finding and beating all the Bosses in the solo dungeons there. Contains
tons and tons of Spolers.
* How do you find the dungeons? Oddly enough you need to go enable the "Points of Interest" option on your map while in Cyrodiil and then they'll all appear. They are disabled by default.
Dolmens/Dark Anchors
* You will be delightfully surprised that the easiest Dolmens in the game are those in Cyrodiil. You can easily solo them. I've yet to get ambusehd by enemy Alliance players at one.
* They don't show up on your Map as a Point of Interest, but you can generally see them on the map as circular-shaped things. Realistically, you're likely to eventually stumble upon them due to their habit of having 1000' tall anchors hovering above them that emit loud, attention-catching noises.\
* If you run into Cloud Ruler Temple in the far Northern mountains, it isn't a temple and there's no quest associated with it yet. Also, so far as I have gleaned from many Google searches and asking around in-game, there is currently no way to get in. Just going there turns the "Point of Interest" on your map from black to white, although unlike in other zones there's no achievement for visiting all "striking locales."
Quest Hub Villages (how to put the finishing touches on the Tamriel Hero title)
* There are a bunch of towns on your list of prerequisites for the Imperial (read: Cyrodiil) quest Achievement in your journal. Unlike the PvP objective locales, they do not appear like a normal town on your Map. Nevertheless, unless you simply Google a map of where they are, you're likely to eventually be directed to them by one of many out-of-the-way quest-giver NPCs which ask you to deliver something there scattered all over the place, often repeatedly.
* The first important thing to know about these towns is that sometimes they get allied with an enemy faction due to PvP objectives in the vicinity being taken over. The only danger there really is that the NPC guards which patrol around may notice you. Check them from afar and see whether they say "Pact Guard" or "Dominion Guard" or what have you. Then just learn their patrol pattern and scoot by to talk to the NPCs when they've wandered away. There is also a higher chance of enemy Players being around when they control the quest hub town, so just be cautious. You can always just watch while stealthed for a while and see if anyone's around.
* The next most important detail to know ahead of time is that there are two different types of quests in these hubs: quest-lines and repeatable daily quests. The repeatables are presumably for PvPers who know that the VR++ areas are too dangerous for l33t d00ds and thus all XP must be earned within the confines of Cyrodiil. The quest-lines will not be dailies, but
some of them will appear as the ones you're trying to tick off your list for that particular town as listed in your Journal under the Achievements tab. Those are the ones you're after, and the others can be ignored unless you're farming XP, but be careful not to do them repeatedly and waste time if that's not what you're after, as there's so many of these that you might not realize you're doing something you've already done before til you've run miles and miles away... or not even know why they're asking you to do the same thing again, as it's not like the NPCs come straight out and tell you that you're doing a repeatable, daily quest.
* Sometimes these quests send you to a place where there's a Boss intermixed with the trash, so just be careful to notice the ones with the bling all up on their nameplate. This is also true of the occasional, non-storyline Bosses that don't have any particular quest or achievement associated with them in the Overworld, as opposed to within dungeons, for as far as I know all of them have Achievements or quests associated with them there. (I'm not 100% sure about this, for instance the boss Troll in a tiny cave in the north mountains near Cloud Ruler Temple, as I may have just not stumbled on some daily that sends you on a quest there).
This Guide may be edited, updated or added to as others add things I overlooked.