One of the biggest issues with playing tabletop games is finding a group who will enjoy and play the same games, and who won’t try to kill each other when they share a room for about three hours, which is what most sessions run, if not more. As a new player, you should almost always join a group that someone else is starting or has run for a while, but occasionally you’ll find a GM but need other players.
There’s really two good ways to figure out a group; contact a friend who you know (or suspect) games, or find a Looking For Group invitation on a service like Roll20. Either way, you should be able to figure out pretty quickly what you’ll be playing and the people you’ll be with, and then make some educated decisions about it.
The first step to finding a group is to make sure that your group would actually be interested in playing the same things. Your SCA chapter may be full of people who want to enjoy jousting and feasting, and would be open to playing something like The Dark Eye or Dungeons and Dragons, but they might not want to play Shadowrun or Cyberpunk 2020. Needless to say, you’ll need to make sure that your players are interested in playing what you’re interested in playing. My advice would be to keep track of every group looking for members that you know people from that you’d be willing to play with, but focus on a game you think you’ll enjoy. Ask people how much time commitment is involved in a game; if it requires a lot of bookkeeping and nobody is willing to help you, it may not be a good idea to start off with it, but genre is often the most important thing in figuring out what you’ll like; if you hate soft science-fiction with all sorts of loopholes and implausibilities, you might not want to play in a Star Wars campaign.
The second step is to make sure you’ll get along with your group. I’ve run some pretty big groups, and it’s typically the GM’s role to do this, but there are a few warning signs. For one thing, try to figure out everyone who’s in the group (if you have a friend in a group, you can ask them, and online sites typically post it up obviously). If you can sit in on a session with a group, I’d recommend doing so, so you can get a feel for the dynamic; if they take time to explain the rules to you and there doesn’t seem to be anything going on that you don’t like, they’re probably a good group, but if they’re too raucous for you or they don’t welcome you as a newcomer you should think twice about joining.
Avoid groups with high-tension out-of-game relationships. I always let all my players vet incoming players beforehand, but as a general rule any time an ex joins the table it’s bad business, as one or other member of the former relationship decides to hold a grudge or escalate things or otherwise disrupt play; in addition, be on the lookout for inequitable treatment. I’ve known a lot of groups that are pretty close knit, and while they don’t turn away newcomers explicitly they don’t welcome them and you’ll have a less than optimal first-gaming experience with them, though I’ve never joined one or run one myself.
Consider your own availability. If you can only make a few sessions, make sure that they’re okay with it; I ran a game with nine players once, so we definitely had better sessions with a couple people missing, but if there’s three other players and you miss every other week the game will be pretty seriously impacted, especially in a game with heavily stratified character roles (again, D&D). Be sure to be clear in your communications to the GM and other players about circumstances surrounding when you might miss sessions. Of course, we all recognize that life happens, and GM’s can be pretty good at adjusting on the fly for missing players, so don’t feel too guilty about joining a group of your friends on an occasional basis if they’ll have you.
However, sometimes you’ll be building a group with people you don’t know. When I first went to college, my Shadowrun group consisted of a friend of a friend who brought up D&D and then his desire to play Shadowrun in a conversation, and I mentioned that I’d be willing to run a game if he found some people. Three days later, we had a tentative list of players, most of whom showed up on the first day and stayed through the whole school year, of whom only the two of us had ever seriously played on the tabletop before.
So, in short, finding a group is really about relationships and confidence; if you’re dropping into a group make sure that you can fit as part of the dynamic, and if you’re working with a GM that you’ve found to start one, ask around until you get enough people. Come back next week for advice on making a character once you finally get a group together.