The second most important thing you can do is read the rest of this site. There is information here for players of all skill levels and experience. However there are a few things that you'll want to check out that we'll cover here briefly. These are clan tags. They designate the player as a member of a group of players that game together.
Clans often compete as a group on several of the gaming ladders out there.
While not everyone is in a Clan, and not all Clans compete, it's not a bad idea to have a group of players you game with frequently. That way you know the kind of people you're going up against. The clan tag also aids in finding your fellow players out there on the thousands of Internet Servers. You'll see a lot of players talk about connection speeds, ping, lag, etc. That's because a fast connection is the holy grail of the Quake world.