Well you have to meet people and get them to listen to you play either live or via recording. And I think they look more for people that make the right musical decisions in context to the music Vs someone with over the top, out of this world chops. Get a good portfolio together with videos or mp3s that really showcases you as a well rounded musician.
Agreed on the making musical decisions part!
Disagree on the video/mp3 thing, though. It's just too easy for a bandleader to find something he doesn't like. You'll be playing too loud, or too soft, or be dressed too nicely, or not nicely enough. The bandleader has his regular drummer in mind, or someone famous, and his image of what he wants will only solidify if given the opportunity to refuse something unlike it. Besides, what makes interesting video footage of a drummer is usually very different from what or how you'll be playing on the gig. Conversely, if your video is too practical, then it may become boring, and cease to serve as an effective marketing tool.
Musicians are very quick to box you in as a player, too, especially if they themselves are young or narrowly focused. If they see you on a rock gig, to them, you'll be a rock drummer. Jazz gig, jazz drummer; big band gig, big band drummer; latin gig, latin drummer; blues gig, blues drummer, and so on. It can be difficult to break out of this. Sometimes you even have to create the gig (assemble the band and book the club), just to prove you can do something else!
What gets gigs is being competent, unfailingly nice and humorous, and (in the words of Shawn Pelton) not being a pain in the ass! Respect the music and the bandleader's vision for it. When you do get the call, always say yes, yes, yes, and realize that, to get ready for the first gig, there will be a huge amount of work to do for a small amount of money, but then not so much work and the money should be the same or get better.
Solid, confident time-playing is non-negotiable! The drummer's first responsibility is to keep the ensemble from speeding up or slowing down, because this is what makes the other players (and audience) feel most comfortable. Everything else (style, feel, volume, image, sound) depends on the situation, so let your knowledge of the music and the people creating it, and not your own desires, guide you.