Depends. If I have the AV talent I tend to keep it rolling on the tanks to make sure they always have the AV buff. Otherwise I tend to just put it on whoever needs it the most/going to need it the most. I find it’s something you get a feel for with time and practice.
I found proving grounds useful for getting used to a new healing class in a stress free environnement. It’s how I got to grips with resto druid when I decided I was going to give that a whirl. Even though you don’t use the same talents for PG as you do raids, as a general rule, I do find it gives you practice and a feel for the toolkit of a class and you can try out different talent set-ups and interface changes etc.
I personally use weak auras. There are some here on chainheal.com you can look at, I’ll probably get a picture up of my own UI at some point today if you’d like to see what mine looks like.
Anxiety can have an annoying habit of doing that, luckily it’s something that gets better with time though 🙂