From my (albeit limited) experience, it only works if you have a break, like a time when you don't speak to make sure that you're both ok with it. Then, if you're meant to be friends you'll drift back together as friends. Don't force it. I think it's kind of impossible to do straight from a relationship to being friends...the one time I tried this, it ended up getting verrrrry messy and emotionally confusing.
I think it depends how invested in the relationship you were, how long you were together and the circumstances surrounding your break-up. I'm best friends with one of my exes, but my most recent ex I can't talk to.
definitely depends on how long you've been together and how into the relationship you both were. i find there's always some awkwardness to start off with but it gets better the more you talk to them and are around them. so if you'd see them a lot anyway and you were friends beforehand you can probably still have a good friendship afterwards.
I prefer throwing them in the dustbin of history where they belong. No matter how nice they were, I don't want to be friends with them ever again. Strikes me as pointless and stupid when theres so many other people on the planet you can get to know instead......
Depends why its ending, how they find it easier to move on... I've not stayed friends with ex's, would like to see how they are and stuff but always feels a bit random to message them out of the blue :|