For most abilities, using a light attack and immediately using an ability while the light attack animation is just starting will serve best. There are some people who like to weave in light or medium attacks after channeled abilities like Sweeps/Jabs but I have never seen any results from doing so. Of course, I could just be doing it wrong, and am open to being corrected on that by more experienced players.

But for the most part, LA before skill activation will increase output in most situations. It's so fast that, if done properly, you basically don't even see the LA animation. We on the PC have the advantage of scrolling combat text and so we know that it's working. Until you have it on console, assume that if you hit LA and cancel it with a skill, it went through. It's very consistent.

It helps to know about the priority system. Actions in the game have different priorities and an action with a higher priority will animation cancel an action with lower priority. Light and heavy attacks have the lowest priority followed by skills and then block, bash, weapon swap and finally dodge roll. In pratice this means that any action will cancel the animation of light/heavy attack, but only block/bash/weapon swap/roll will cancel the animation of a skill. With this in mind it's only possible to animation cancel by using light/heavy attack before a skill. A typical animation cancel rotation would be LA - skill - tap block/bash/weapon swap. Tapping block is important because a long-hold on block will cause its own animation that is hard to cancel. Dodge roll can be used to animation cancel when taking damage but will always cost stamina so isn't ideal for regular use. Block and bash only cost stamina when making contact, so using these to animation cancel is free unless you're taking damage. Hope that helps.