I like things to be compact.

The very bottom hotbar's hotkeys are 1 to 7, middle mouse button, Z, X, and two buttons I have on the side of my mouse.
The next two hotbars are all the same hotkeys, but Ctrl and Shift respectively.

My rotation always goes in 1-7, but I use 7 rarely and 6 is reserved for things used less often. I should probably move acceleration, but I'm just so used to it there that I'd mess myself up.
On Z and X, I put utility, buffs, or anything fitting that general description.
On middle mouse button, I always have my potion as ctrl, my duty action as shift, and the last slot is reserved for a cooldown that's more conditional in use, such as manafication.
On my side mouse buttons, I like putting damaging OGCD abilities.

With my hotbar structured this way, I find it super easy to preform my rotation, because I have my left hand completing the rotation and moving to the next skill while my right hand is doing most of the ogcd weaving. My left pinky is MVP, though, for always hitting ctrl and shift.