Given a small number of mutually exclusive choices (as in a multiple choice or true/false exam), how do you determine the one that the creator of the question intended without knowing enough about the specific subject?

• In general, the second highest numerical answer is right about half the time.
• When there are all-of-the-above or none-of-the-above questions, the person writing the test will choose the all/none-of-the-above choice either very rarely or above 50% of the time. Thus, if you know that the answer to one all-of-the-above question is "all of the above" and have no clue on the current question, "all of the above" is probably your best guess.
• Surprisingly frequently, wrong answers don't fit grammatically into fill-in-the-blanks type multiple choice. If it's not grammatically correct, it's probably not the right answer.
• Read the entire test before you start answering questions. Frequently, answers to early questions are in later questions. Here it's a good idea to learn to read at least twice as quickly as the average student so as to be able to do this with any fair time limit.
• If two options are the same, they're both wrong. If one is the negation of the other, one of those two is correct.
• Always guess. "Guessing penalties" don't actually penalize you for guessing, they're designed to offset random guessing on average. Your guess is probably better than random.
• Unless you can point out the specific way in which the answer you gave first was wrong, don't change it. It's very hard to think "this answer is probably wrong" without thinking "this alternative answer is probably right", and so while your current answer is likely wrong, your next choice is likely to be worse.
• If an answer contains qualifiers (may, might, sometimes), it's more likely to be correct.
• One strategy I have heard of but not personally used is to treat multiple-choice questions as a series of true-false questions and pick the "most true" answer.

You're not going to go from random chance to an A with these techniques, but you might go from random chance to a 70% or from a 70% to an 85% (my ballpark estimate is that half of the errors the average person makes on a test are avoidable with the use of heuristics like these).