Why do my bike brakes squeak?

Why do my bike brakes squeak?

I got a new bike yesterday and the brakes squeak. It's not a loud squeak, but it's loud enough to be annoying. I've already dried the rim off, and it helped a little, but it's still squeaking. Any help?

Thank You

 

The most common cure for rim brake squeak is to set the pads with a bit of toe-in. Apart from that it can be an endless chase, from brake mount to headset to...well, whatever.