Vendor Scorecard

I was recently given a project to rate all of our IT support vendors. I was asked to first come up with a way to rate them, create a scorecard, if you will. I have no idea how this scorecard should look or what the content should include. We have vendors ranging from Dell for equipment purchasing, Qwest for IPVPN and AT&T for remote access (dial-up internet). I need a scorecard that will cover all vendors. Any suggestions?