Check out each forum and just start participating in forums that you think sound fun! You could:
-Apply to be a LSU in an ongoing RPG, join one with signups, or look into starting your own by contacting a mod there for more details.
-The Anime-Style Battling and Adopted & Captured Pokemon games are fun if you're into Pokemon and want to interact with other members in a way that lets you use both strategy and your imagination. Contact Lady Vulpix if you're interested, and she can orient you to the games. It's easy and fun, and a great way to meet new people with similar interests!
-You could start writing a fanfic or create some fanart. You can bounce ideas off other members, or just start creating one. Hint: One "don't" would be to post a few sentences in a new thread detailing what you would "like" to do and asking for opinions. There's a writer's lounge for that
-The "Games, Games, Games" forum has great games, some Pokemon-related, that you can jump right into and start playing. Just make sure you read the first page of a game if you're interested, and start participating if you get the gist of the rules and how experienced members play. You can even win prizes for your signature!
-There is a group you can join called the "International Club" if you're interested in interacting with members from your country, state or even city, or may speak your native language if English is not your first one. If you're from Virginia (your location says "VA"), there are a lot of members from there!
-If you have a meaningful answer to an unanswered, recent question in a video game-related thread, a great way to get involved is to walk the questioning member through a solution.
-If you have experience working with websites, or have a lot of knowledge on Pokemon of any generation/incarnation and want to help expand what we have, contact Jeff. He is very involved with maintaining the website.
-Finally, read a few threads in Misc that seem like both in-depth debate and also ones that have much casual chit-chat. You'll get a good idea for the levels of snarkiness and maturity that are the norm for those threads. Note that people who act snarky towards one another are usually people who have been here for a while and know each other well enough to poke some fun. Flaming is prohibited.

If you have any questions at all, just ask! Enjoy TPM