Guessing you're in High School? Your best bet is to just start asking everyone you know if they know anyone who sings/plays anything. Start hanging out with the musicians. Maybe even post some flyers up for "auditions".
Craigslist is another option, but I don't know how well it works for a start-up High School band. You generally get people a little more experienced there and the experienced ones aren't going to want to waste time with a start up band.
