Scan the entire test first.
Do those problems which appear easy first. Go back to the harder ones later. Problems which at first appear difficult may seem easier on the second reading.
Never leave a multiple-choice question blank unless you will be penalized for wrong answers. Try to use process of elimination to narrow down your choices.
Do not be intimidated by classmates who leave the test session early.
Check your work if you have time. The easier problems especially should be checked for computational errors, miscopied numbers, or any type of mechanical mistake.
Learn from your mistakes! Do not throw out returned exams, but correct every error, then keep the test to prepare for the Final Exam.