We should decide some things, first.
1. Do we want this to be a shared universe for all members, or do we want it to be a venue for people to write whatever stories they want, in whatever alternate universes they want?
I'm leaning toward a shared universe, but I'd like to see what everyone else thinks.
2. Original characters--I think it's pretty obvious that original characters are welcome, if not preferred.
3. Before or after Deathly Hallows?
4. If post-DH, should it be canon (Snape is dead) or AU (Snape is alive because he's more fun that way)?
5. If Snape survives, how are some things different? He won't necessarily have given his memories to Harry; I really think that was an act done only in extremis. He wanted Harry to know the truth, at the end. Would he have shared all of that for any other reason?
A work-around, if desired--Snape thought he was dying and gave Harry the memories, but he was more resistant to the venom than expected and was able to get treated in time.
6. Do we want to call ourselves anything, or just stick with 'Potterish Writing Group?' (There's gotta be a better name out there.)