Best tip I got was to move my movement keys over to the right one row. So:
strafe right R
strafe left W
This opens up more keys to the left. I think I could probably dps (on some classes) with only a few keybinds, but as a tank or healer I need more keybinds. Keybinds include
1,2,3,4,5,6,mousebutton (side), f,y,q,a,z,v,t,~,x
Shift mods for all (if you're comfortable).
It doesn't have to be exactly that, but keys you are comfortable reaching. All my characters share keybind concepts, such as spell interrupts on Y, main attack/heal on 3, instant cast dots/hots on 4 and mousebutton, dispels on Q (if healer) or 7 (if dps). So when switching characters you can pick up the play style easily. If taunt is always 2, then that's one less thing to relearn. With active mitigation tanking, having your resource dump mitigation abilities on easy to hit buttons really helps.
I would also recommend some type of addon setup that concentrates information in one spot. I personally use Shadowed Unit Frames (self, target, target of target, target of target of target, focus, pet) and Classtimer (self and target). I have everything center/low so that the screen is mostly open and I can see everything at a glance. You don't really need a threat meter front and center anymore, but I find it useful to have off to the side. If you keep all your action bars showing, you'll want a cooldown on the buttons (don't remember if Wow's default does this anymore). I like CooldownButtons because I can have them all in one spot, but again that's preference.
For tanking, Tidyplates is very useful. I would recommend a raid frames addon if you're comfortable setting it up. For a tank, you don't need much, but keeping it to the side and out of your vision helps. Vuhdo (takes a little setup), Grid, etc...