What Goes into Anthology Editing? What Should You Be Aware of?

Sometime in the next week or so I'll post some thoughts on editing anthologies.

But I thought it would be interesting to get some feedback from readers first, in answer to any or all of the following questions. You can note whether you're referring to original or reprint anthologies if that's important for context.

(1) What do you personally look for in a fiction anthology?
(2) What do you feel are the top five constraints on anthology editors when putting together an antho?
(3) What do you...