Knowing what to A B test

I came across information about A B testing. A B testing involves two scenario web pages (usually a design change), that are equally presented in front of web visitors. You can then use analytics to track the behaviors of the two groups and see which design results in higher conversions or achievement of your goal. (whatever your goal with that page is).

Example:
You have a button that says “Register” for your web service. But you want to test “Sign Up” instead.
You can use a service to show half your users one page with the “register” button and the other half of your users one page with the “sign up” button. Then you see which one is better.
Once you determine the wording of the button, next you can AB test the color of the button, or the size of the button. You can keep doing this with all the things on your page until you have the ultimate conversion page, that utilized your real users, with measurable results. See Smashing Magazine’s Web Form Design Patterns for their stats on sign up forms.

But sometimes we don’t know what to test for. Which Test Won, is pretty cool paid service that lets you see what others are testing, and see which AB test performed the best on that company’s site, and may give you some inspiration for testing on your own site.