OK, so before anybody gets all upset by any comments I make below, I am an absolute novice to pvp and what I suggest may be completely wrong. No worries. This is just my early impressions and ideas. Beware - Long Post
Enough prevarication, onwards! (which way? - a recurring theme in pvp)
For those of you that haven't tried pvp, don't be shy, it can be fun. That is if you don't take things too seriously.
Last week I thought my latest toon, a templar, was murdering the pve content. Soloing World Bosses in a level above my rank and soloing dolmens with named leaders. I made VR6 in about 2 weeks and thought, right, I'm going to give cyrodill a good seeing to. A guildie gave me a tour on an AD toon and I liked it.
So still in my pve gear, with pve skills on my bar, I joined Thornblade as DC's latest recruit. Now when you first arrive there is nobody about that will give you an easy ride. Pvp is populated with VR14 hardcore nuts and clueless wonders like yourself. Most of the time you will not know what is going on - First point
Let it Go - You are not in control, it will not react like you are expecting, you will get owned and not know why. Just embrace it an move on.
There is a little quest you can do, play with some siege stuff and get some freebies. Well worth doing. Then, if you have unlocked the bounty hunter trait, you can pick up a kill mission. OK sorted, lets go and sort out the AD and EP axis of evil.
Lingo point - Smurfs = DC, Bananas = AD, Tomatoes = EP. So when somebody yells -Tomatoes in the woods being chased by Bananas!! - you don't sniff your drink.
Lots of guys typing lfg, Look for Group, I have no idea if they on my side or not and so I just do the same. Now after about 20 groups I feel a bit of a veteran. You don't get much info from group, and there's nothing resembling a command or rank structure but, hey ***, I can follow them on the map and at least know where a fight is. I was following one guy, a VR14 corporal, and he was following me as he thought I knew something. Hilarious.
So you have a curious state where you are watching to see what folk do and if it takes your fancy doing the same. This can lead to some comedy moments like a silent movie.
Next up some tactics and lessons learned via dying a lot.
First off, if you have a siege projectile weapon, don't aim it at the door. It also helps to aim it where other folk are aiming there lobbers.
Healers - you can earn loads of points with a crafty healer - I am surprised nightblade healers are not dynastic emperors.
Next handy hit, always pack a Camp, or forward command post as they are known. If you res and the tent disappears, set yours up. Don't moan in chat about the lack of a camp if you never bring one.
OK - Moving on to my gear and skills. You will get hit a lot, so pack the best armour you can. You will need protection from criticals.
Getting the Horn - Having the horn gives you 500 health, no idea on the how or why of this but getting the horn is a huge plus.
Stats and skills - Now I arrived with kit designed for spell damage and 10/39 health magika split with a resto staff and sword and board.
I still have the resto staff, and the shield but my kit has been swapped out and I am seriously thinking of going 49 health, or even 10/29/10. Why? Da f... you say?
Simply put I run out of stamina most often, especially if they packing a lot of DK's with talons. My overlordship of pve was based on damage output. This isn't pve so I need a bit of a re-think. That's still work in progress.
I have tried the blazing shield, blinding gizmo's etc that templar threads rave about but I died faster than with just immovable and don't have the health to hurt with BS.
So I use the healing stuff on the staff plus rapid maneuvers, a nice anti CC tool, and on the shield bar I use all sorts of nonsense to try to confuse the bad guys but always magelight. I don't care about the crits it's the detection that is golden.
Tactically I try to find a DK that has waded in and looks a bit low on resources,note, these guys pack an absolutely epic tank so engage them knowing that. Sometimes I hide and wait for a NB to try something sneaky and jump him when he's not looking etc. Sometimes you just wade in for the hell of it. Sorcerers are pesky with their bolt escape and if you can find a templar then you are in with a chance of him being as bad as you.
Sneaking is king, blocking and rolling a must. If you can then pick your targets. If you can't then die hard. In fact either way die hard.
This is important, if the bad guys are wasting cycles killing you then they are not running rotation on your buddy. So spam that heal, block like a king, roll, dodge, anything that ties them up. Most of the time you are not going to get away and win, you are going for a tent trip. So make it count. Your group may kill that annoying batswarming sucker after all

So TL:DR
new gear, cc kills, don't stand there, and your pve skills suck
I'm having a ball, not a clue but it's furious fun