Well, I know my response a few posts back didn't really pertain to the original question, it was just something that kind of jumped out at me from the comments on scouting. But in regards to the original question...

1. entry and egress routes
2. wind. It is a huge factor up here on the plains, especailly since there aren't that many trees for tree stands.
3. choke points on travel corridors
4. not in particular certain events, like the rut, but specifically the timing of those events. What I mean is, not necessarily just the right place, but the right place at the right time.

Thses things are general, I know, but they change so much according to the situation.