John,
I can't tell from the limited amount of information from your post if you are coming from a power source, or from the light, or from the other 3 way switch.
Between the two switches you will need 12-3 not 12-2.
But a web site that should be a help to you in more detail is:
http://www.handymanwire.com/articles/3wayswitch.html
Good Luck!
Dodgeman