I think I saw you jump into a few RP's here and there, so that's pretty neat so far, I think
Well, things to look out for would be like any additional rules (besides forum rules) that the OP (original poster) might have set up, any storyline or other details they might have written up as well, and see what their wishes are. Generally with Fun RP the RP'ing rules are more 'free' compared to Serious RP. Serious RP's usually focus more on story-driven stuff, proper grammar and spelling, etc. The posts are usually generally slower but longer.
So that, I hope helps? ^^