Basically, try to keep relatively cannon (within reason since obviously characters are unique and your own and of a new generation). But the only way to find out is to fill out the profile and send it to a GM for approval. If there are issues they'll be discussed and things can be tweaked accordingly. But it's fine to have rivals and other such things added into the mix of the population in the group game. So have at and we'll see how it goes.
Ohhh and the only other thing.... just comply with site rules. That's the other biggie. But that's probably pretty obvious too. XD
In the mean time, after you send in a profile, just be sure to read over the various stickied threads and such as you want to be up on the rules of the group game and everything. If you need any help a GM will point the way.