How to wire 2 way switches that will control one ceiling light
If I understand you correctly, they are actually called 3 way switches. I did a google on 3 way wiring diagrams and came up with the link listed below (along with many others). Choose the diagram that describes your situation relative to where the power enters the loop. Follow the directions carefully!
Here's another http://www.wfu.edu/~matthews/courses/p230/switches/3way/variations.html