About restrictions:
I strictly dont use Barrels, like ever ... with exception for tutorial final battle.

I never use non-Wizard spell with my Wizard (or Gale), even tho i often learn them, not even as a scroll.

I usualy dont use resistance potions ... but that is mostly bcs i usualy forget about them.

Same goes with diping ... i almost never use it, since i forget quite often ... i do use poison for my rogue tho, so im sure how to count this point. :-/ I never dip from candle, bcs i find it ridiculous.
Back in the days when that was possible i never eated during combat, allways out of it.
I never inspect enemies before combat to find their weaknesses and adjust my gear for them ... i just go with my curent build and hope for the best.

I rarely switch weapons back to meele after ranged attack so i can use AOO ... but that is usualy also bcs i forget.
I almost never throw potions, healing or other ... since i find that huge waste of action.

Also alchemist fire or simmilar, but i usualy just forget on them.

I rarely shove, since i like to have loot ... with exception for Crusher, him i shove allways. :3
And about homebrew:
I often position my party members for ambush, before i go to talk with some NPC (some would say metagaming, but i did that on my first play so ... w/e) if i get first in initiative, i often use option to freeze enemies in combat and sneak to better position.