STUDY THE FIRST TEST BEFORE YOU TAKE THE SECOND: More than most courses, MicroEcon builds on early material. Even if tests aren't cumulative, the skills you learn early in the course will still be needed later. Always review your prior tests and homeworks as part of your study.
DON'T REVIEW ONLY WHAT YOU MISSED: Even if you got a question right on a prior test, you may not remember it as well as you think, or maybe you guessed and were just lucky. If your tests are multiple choice, be sure you understand why the right answer is right, and why the wrong answers are wrong.