Im not an expert, as I have stated many many times before, but I believe the +hit to spells cap for warlocks is something about 206 (not exact, but its around there) so I suggest getting +hit as much as you can, untill you hit that cap, BUT DONT WASTE YOUR TIME AND OTHER GEAR JUST TRYING TO GET +HIT CAPPED.
+Hit is important because it helps your spells land always(or most of the time) so you dont waste so much mana and time re-applying DoT's/casting SB/etc and so your total dps is higher, I believe in terms of that and dps it kinda goes in the way of "+30 hit rating = 24 spell damage" now I know that is not accurate at all, but at least you get the point of what I mean.
Then obviously the most important part for a warlock is spell damage, why? well because it just makes you own stuff that much faster, 'nuff said.
Now +crit is a tricky one, with destruction being its obvious best friend, because the only dot you will put up is immolate (and maybe corruption) and you will just throw spells very much like a mage does at the target, it also depends a lot on builds, and you definitely need to post your build, wether its mostly Aff, or mostly Destro.