Welcome to Gaia! biggrin I don't remember such threads existing when I first joined Gaia - like back in 2004 I guess. Man, that was a while ago. I haven't been on Gaia in a while, but I presume it's still the same. Role-plays are both fun and addicting. In fact, I found Gaia to be the best place for role-playing. I haven't done it in a while, hence probably why I haven't been on Gaia in a while. Anyway, choosing a role-play is like researching a role you may want to audition for.
When choosing a role-play, I first look at the story and plot of the role-play to see if it's a good fit for me (whether the story is interesting, easy to follow, and doesn't seem to be short-lived). Then I review the rules and guidelines set by the creator of the thread. Most are generally the same, but it's still always a good idea to check. Then, if there are already posts, I skim through the posts to see if something worthwhile is brewing. If after 5-7 pages of posts prove to be lacking in a direction of story, then I won't bother. It still depends though. I also look into the character of writing of other role-players through their posts. If I see a lot of people writing short, ridiculous (sp?) responses, then it is a definite NO. Lastly, I always check the grammar of the creator of the thread. If their spelling and grammar is way off, then they are most likely going to attract other rps just like them. Also, I wouldn't recommend any rps that already have 100s of pages of posts - it is very hard to determine where the plot is in the story and sometimes you end up being ignored by other rps because they are in the middle of their own story plot and have no room for you - at least not for another 20 pages.
Always, always, always send in your request to join an rp first! Do not just jump in and post. I recommend trying a few rps before ever starting your own - unless you already deem yourself an expert. I've started probably 3 or 4 and they have been successful. But that's in the past. Oh, you can also do one-on-one's if you can find the person. I've done a couple - mainly when I'm bored or in the middle of a chat with another gaian, especially while waiting for updated posts for my other rps.
Probably unnecessary information, but I hope it helped.