Re: Greetings, I'm a newbie :)
Hey, fantasy, good to have you! I'm pretty laid back about grammar myself, but I've been known to ask for punctuation and a quick spell-check from time to time. =) I agree with you that playing by post can help people develop into better writers. I've seen it firsthand myself.
The first places you should check out are the Help and FAQ files in the upper right. The information there will tell you pretty much everything you need to know about playing on RPOL, including how to find games to play, how to run games, and the site's rules. In addition, each main forum has its guidelines detailed in a stickied thread to help you know what goes where.
The best place to find new games is in the Wanted - Players forum. Note that some games are rated Adult, so you won't be able to play them until you're 18. Mature-rated games are intended for all ages, and they're more like PG-13 movies, whereas Adult games are probably in the R-rated and above categories. (Here in HK, they'd be Category III movies for 18 and up.) Check the FAQs for more information about these two categories. General games are for everyone.
If you're having trouble finding a game, you can post an ad for what you're looking for in Wanted - GMs. I've also found some great games by doing a site search, located at the bottom of the main page. Just type in the genres and/or game systems you're looking for, and you'll find a ton of games that way, too, although many RPOLians like to start at a game's beginning.
Feel free to ask anything you'd like! The folks here in the Beginners forum are a friendly bunch. Also, please forgive the occasional typo. I'm not 100% error-free myself, but I do make an effort. =)