What do you look for in an RP?

No, I don't want just the general "good plot, good storyline, interesting" schematics. If you're going to answer, please be specific. What kind of RP attracts you the most? Do you like playing as a Pokemon, or a human? Do you prefer an open RP where everyone has plenty of freedom as opposed to one where the RP master is strictly the one who drives the plot? What about the atmosphere? Do you prefer a more upbeat, happy kind of RP rather than a dark, moody, apocalyptic atmosphere? Do you like original-world RPs better, or do you instead like ones that take place in the existing Pokemon world, maybe to the extent your favorite kind of RP is the classic journey-type? In short, what do you look for in a Role-Play? What makes you decide to join one, and not another?