When I join an rp-community (like this one vs another) I look for 1) activity 2) longevity of threads 3) good organization by mods and such.
When I join an RP, I play casual, and understand I am playing a game, so I don't get overly picky about the writing style like on might in advanced games. What I do look for is 1) Inspiration, the rp story just gives me an idea for a character . . . 3) I like games where there it seems like roleplay and character interaction is of importance. This impression is given . . . form the GM and the plot . . . If everyone is just a bunch of combat stats, I am turned off.