Depends on the draft class. Last few allocations I've done, good OL depth is hard to find. I usually like to fill out my entire starting lineup before I go into drafting much depth. Once the starters are set, the rest depends on who is left.
I prefer not to have a set plan too far ahead of time, unless I'm going to work and I need to fill my queue. If you're too dead set on a single position, you could miss a player elsewhere who could turn into something great.