Ah, so this is what you were using our suggestions for.
Well, when I go looking for a role-play (let's say I'm looking for a long-termed one) it must have a site or a forum (can have both) which must be organised (I cannot stand disorganisation), the concept of the role-play must be interesting, and if it's unique along with that, then all the better. I'm sick of seeing warrior cats on every corner. It has to be literate (occasionally I can cope with semi-literate, but no less) and active (more than one person on every day) and it is imperative that it has a good map. I will have a go at a role-play that a friend has introduced me to, but someone just randomly offering me one is unlikely to get me to join.
If I see a short-termed one advertising in Fluorite (it must be literate) I may join it if I'm in the mood. Otherwise, unless the plot is irresistible, I will not join a short-termed role-play.
I'll make my answer short, sweet, and simple.
Long term Roleplays.
Because they are quite fun and allow you to develop an interesting plot within them.