Here is a screenshot of my user interface, courtesy of Harrylime.
I don’t use a UI mod like Pitbull or Xperl – I tried them – but I am happy without them. The biggest difference between my UI and the standard look comes from Bartender3, which changes the action bars.
Bartender (and other mods like it, e.g. Bongos) allows you to modify your action bars, resizing, reposition, and increasing/decreasing the number of them. You can also stack them vertically, as I have done on the righthand side with my bag bar and micro menu bar.
It can be a bit fiddly to use at first, particularly if you have several alts, but its easy to set up once you have the hang of it. The only things I don’t like about it (and may be this is because I don’t know how to use it properly – so please post a comment if you can solve my problem) is that firstly I cannot seem to lock action bar 1, and it sometimes flicks around (like the shift + 2 of the standard action bar) to display another action bar. I don’t know what key combination I am accidently pressing to do this, but it invariably seems to happen when I am desperately thumping keys in the middle of a BG and wondering why none of my spells are working. The second thing is that the exp bar loses its sub-bars, so you cannot see how many bars to go until you level. And the final thing is that you lose the little red lag bar you get in the standard UI (although Fubar and tinystats both have replacements for that). All in all though, I find this much better than the standard action bars.
Just to neaten up the bottom of my screen, I use skinner, which puts that black rectangle behind my action bars breaking them off from the rest of the screen.
Also on the skinner section of the screen, I have a small chat window to the left of my action bars, and a small recount (damage meter) window to the right.
I have Omen someone on the screen, for Tinuviel when raiding, or for Bluebear, my bear tank, this is in a very prominent place.
The improved casting bar, Quartz, appears at the bottom middle of the screen when I am shooting. While the cooldown timers, appear down the sides of the screen, showing when abilities and trinkets are on cooldown.
Fubar at the top has lots of little addons, you can choose the ones most useful for you from the Ace website.
That’s all on my UI. But if you are thinking of changing your own UI, go check out the screen shots of players UIs on WOW insider. This is what I did when I decided to revamp. I found one I like and adapted that.
(Hehe, I just noticed Holly needs feeding! I also noticed he has both bite and claw turned on. I don’t play Harry much at the moment, but Tinuviel could tell him that Holly would have higher damage if he stuck to just claw.)