Maybe many or most of you do this too, I will actually take the test that I'm to admister before I give it to the students. (they are premade tests that never change). Usually we have 5-7 tests in period of 5 weeks. I try very hard to do it well ahead of time as I'm preparing lectures. This really helps me to 1) find errors! 2) know what points really need to be highlighted for the students and 3) determine the level of difficulty. Then I check my answer ket with another instructors answer key. I have found when I've slacked off on this, I had more errors in my grading of tests, and not as good of lecture and information to give the students.