1 - Someone has to Edo Tensei you first. (Since Edo Tensei only works after you're dead.)
2 - That person has to allow you to do it.
3 - You must know how to use Edo Tensei.
...I can see why nobody else ever thought of doing it, is what I'm saying. Given that there are all of four (five if Tobi knows too) characters who know how to use the damn thing.