It's one thing to respond to a band looking for, let's say, a bass player. It's a whole other thing to actually get the gig. Chances are, a whole bunch of people replied to the flyer that band put up—especially if their music samples are good—and you're going to have to do something to differentiate yourself from the masses.
This is an age old issue, the need to enter a saturated marketplace and define yourself—or, more to the point, your brand—from all the others. Let's face it, there are a lot of good musicians out there, and not nearly as many really great gigs. The question is, when you find a gig you want, what will you do to make sure you get it instead of the other guy?
First thing's first.
Their very first impression of you is going to be the message you send about the request they made for a bass player (or whatever). Make no mistake, the judging starts here. Human beings always judge; we use whatever information is available to us and make a determination about a person or thing, and we do it without even thinking about it. The minute your message arrives, game on.
To make sure you get the ball rolling in the right direction, keep it short and respectful. Inside jokes are great, but there's no way to know if the other party got it, or if they were offended, so just play it straight. Say you're interested, send a couple links so they can find out about you and provide some contact info. For extra credit, think about complimenting the music, though only if you genuinely feel that way.
Do you look good when googled?
What's the first thing everyone does when they want to find out about someone without actually meeting them? Yup, the same thing you do. Google is how we do our best to a) find out what someone's deal is, and; b) attempt to make sure we're not inviting a serial killer over for a rehearsal.
So before you reply to that ad, make sure the person on the other end is going to see what you want them to see. Google yourself and make sure there's no weird stuff up there (arrest records and articles about rape trials come to mind). Make sure your presence on Twitter, Facebook and the other social media hotspots represents the image you want to portray. And, of course, get your personal website up to date if you have one.
Be professional.
Assuming they get back in touch and schedule a rehearsal or something, you're going to want to do everything possible to make a good impression. Auditions—make no mistake, that's what this is—are a strange experience for everyone involved. Make it easy by being cool and being prepared.
Learn the material, show up on time, do your best to get a good sound on whatever amp they give you and be easy to work with.
None of that is a guarantee that you'll get the gig, but it's a good bet you'll make it onto the short list. After that, it's all about how you play.
Isn't it always?