Have you done Rabanastre yet? If not, I would likely suggest starting there first. The drops are useful and despite what you might see suggested here, it's actually quite a simplistic raid. The first two bosses require you to pay attention to things but for the most part, as long as you ask for tips from your group before each boss, you'll do fine with a couple of simple pointers.

As far as overall tips go.

Probably the biggest tip right of the bat, make sure your chat window is clear of any combat spam. You'll often see people making calls in /party or /alliance and it's hugely helpful for everyone involved if you can actually see them and act accordingly.

Secondly, at least whilst your starting out, focus primarily on your group and your tank. From there, any spare attention should be aimed at learning mechanics and watching what's happening around you as well as things that are potentially being said. Tunnel visioning hard on the raid frames might appear to be helpful, but it'll get you killed and make it tough for you to actually get a handle on the various mechanics.

If you can dps then that's great, however don't feel obligated to be spamming rocks if you're not comfortable doing so whilst keeping a tab on the encounter, do a reasonable job of at least maintaining your dots and very few if anyone will complain at that.