Let it warm up to running temp. Then disconnect coil, remove all leads and plugs.
Screw in compression tester, and with throttle open let it turn over for 5-10 seconds.
Should get around the 150psi mark, but as long as all four are within 15psi of each other or so you should be fine. Anymore than that indicates a problem, but it wont really tell you where the problem is.

Hope that helps