Read the question and the list of possible answers.
Determine if the question ends in "an" as opposed to "a." A question ending in "an" must have an answer starting with a vowel. The opposite is true for a question ending with an "a."
Check to see if one possible answer is much longer than the rest and also includes important key words and phrases. Teachers often load a lot of qualifying adjectives into the correct answer.
Assess all the possible answers and check to see if there is an "All of the above" option. If there are two answers that you know are right and one that you are not sure of, the "All the above" option might be the right answer.
Choose the best possible answer. Unless there is a penalty for guessing, try to use context clues and previously gained knowledge to answer every question.