do you pit cherries when you pickle them? or not?

Pitting won't affect the flavor one way or another, but depending on whether you are canning/pasteurizing them or just quick pickling them, it can come down to a cosmetic decision. If you are canning them, leaving the pits in may cause the cherries to rupture (the pits expand more under heat). If you leave the pits in, you can try to avoid dismembered cherries by pricking them with a fork before canning. If you are just quick pickling them there's no need to prick them, the temperature shouldn't get high enough to burst them.

agree with Trena: pitting or not is personal preference. same with brined olives from deli. only downside is unwary eaters, so warn people when you serve or give them foods with pits-in fruit. sometimes there are (small) benefits - more flavor when stone fruit are cooked, and you lose no produce in the trimming.