How can you teach yourself to remember the things you've learned when you're under the pressure of a test?

I gave my students a study skills checklist, and one of the items says, “I study enough for my test, but when I get there my mind goes blank.” A good portion of my students checked yes for that one, and I’m not sure how to help them. If you study well and really know the material, what can you do to keep from blanking out when you take the test?

I am teaching math if that makes a difference in your suggestions. The current course is precalculus, but I would prefer suggestions that work for all math classes.