Mark clearly those questions you got stuck on. When you finish the test, run back through and spend extra time on these. Don't change answers. This is the usual panic time and you'll tend to want to read over the whole test. Don't do that.
Most instructors allow time for questions when returning test.
If not, see him individually or in a group and ask for review. Find out why and what you missed. Correct the mistakes. Ask for advice. When discussing your test with the teacher, disregard the grade you made.