way cool! congrats!
band rates tend to scale, depending on the band's success. established, signed bands have money, the rest don't have as much. if you're working with a band that doesn't have much money, YOU will have to manage how much time you put in. the trick is to plan a shotlist ahead of time and shoot to the list.
for example, if there are four people in the band, you'll need no more than 20 images total (3 individual shots, 5 group shots, 3 misc shots). sure, you could deliver a ton more, but what's the point if you aren't getting paid? focus on getting your shots and then turning off your camera. what you don't want to do is go and shoot 500 images in an hour and then spend 4-5 hours going through them, selecting, and editing them, and then giving them a disk with 300-400 images and getting paid $50.
so, you come up with a list of what you're going to deliver before you start shooting.
with this list, you can get an idea of how much time you'll have to put into the whole project. take into consideration travel, parking, hanging around, shooting, processing, archiving, preparing deliverables, and then delivering.
next, you find out how they want to use the images. this should be fairly easy and straight-forward. then you use a stock photo price calculator to determine a base value for the usages. keep in mind, these usage prices are just starting points. depending on the situation, you might have to slide the values down.
once you have all the numbers straight on your side you can see how they match up to the band's budget. you might have to get them to accept less if you can't justify how little they might be able to pay you.
now, there are other considerations. you might shoot more to build your portfolio. you might take less because you're getting into a place you otherwise wouldn't get into. you might hang around a little longer just to make more contacts. all of this is ok, starting out, but you don't want to make a habit of it and you don't want to establish a reputation of being one of those cheap shooters who deliver a ton of stuff for no money.
the most important thing (besides getting paid) is ownership. you will own your images outright, unless you sign a contract transferring ownership to someone else. as you own the copyright, you control the licensing, which means you can dictate how the images can be used. if the band doesn't have much money, give them a license to only use the images on their website. if they want to put one on a poster, negotiate a price for that. if they want to use one on a cd cover, negotiate a price for that. you do want to make sure to spell out that the band can only use the images for self-promotion and that the rights are non-transferable (meaning that if they get signed by a label, they can't give the label the images...the label will have to come to you to get their own license!) you also have to decide if you want to give them permission to put your images on anything else they sell, like t-shirts (you shouldn't do that unless you are going to get paid, too).
you will need to get model releases from the band members in order for you to use them to promote your services, as well as if you want to license the images to others (like magazines, music labels).
hope this help, good luck!