Carefully read the question to find all loopholes, missing words and useful misspellings.
If at all possible, use the trivial solutions and examples.
If you can't be sure, be obscure. Always leave room for reasonable doubt.
Write out the definitions, one after another, and hope that looks like an answer.
Write from the start as far as you can, and then from the result backwards as far as you can. Join the halves without a remark.
Write with a pointed stick instead of a pen. Use pen to write a note saying you had problems with ink.
Dribble a small amount of blood on the paper. Add a sidenote saying “I just wanted more paper. My face hurts.”
Write one of the magic phrases between all lines. (“The lecturer is too hot I cannot think”, “Can't sleep the clowns will eat me” (see Introduction to Coulrophobia, B. Simpson, Springer 2014), “This is not a subliminal message.”, “A set contains in full points that are contained in it.”)
If the class is graded on a curve, bring live bees to the exam. (Or crotcher-badgers. In either case, make sure you are wearing appropriate countermeasures.)
Also, never go to an exam without a bee helmet — better yet, a horned wasp helmet with a flypaper crown — and badger pants. Other people can be proactive, too.
In fact, if there is any suspicion of anyone intending to bring crotcher-badgers to the campus, wear the badger pants all the time. They have very small shower holes around the waist for around-the-clock use.
Just to make sure: detach the shower head, and screw the shower line to the shower hole. Do not under any circumstances try to ram the shower head into the pants, because where it can go, well, you know.
Do not google for pictures. You need your wits for the exam.
If you are in Australia and not very tall or big, beware of drop bears and kidnapparoos.
In the previous case, if you are tall, remember that drop bears tend to gnaw on faces too close to theirs. This is not empty nature advice; many lecture halls have dark rafters, and sometimes proactive people really make notes on where their competition sits.
Find out whether the exam is being graded by the lecturer or the TA. Then, when you hit an insurmountable problem, answer with a torrid confession of love to the other one. Best case scenario: full points after that sheet mysteriously vanishes; plus all-minus-one of the TAs/lecturers are very amused for a week. Worst case scenario: you get a date with someone smarter and richer. (Relatively speaking.)
If you are unfamiliar with the concept of “torrid”, just download a collection of romance ebooks / Fifty Shades fan fiction / anime lemons, strip the text off them, throw them into a Markov chain text generator, and find/replace personal names (at a rough approximation, capital letters after a space not after a period) with yours and the target's. Quality check by turning a parent filter on and off and seeing if anything's blocked. Much should be.
Also: torrid doesn't involve rainforests. Excessive Tarzan fantasies will detract from the sort of torridity you want. Under no circumstances mention Kala.
Tips for grading math exams
The overview scale, out of six points: Seems to have read the question (1p.), answer is correct (1p.), the method seems about right (1p.), the handwriting is nice (1p.), I remember this person from the class (minus 1 to plus 1p.), didn't have to mark anything (1p.).
The err scale. Start at six points, remove one for each occurrence of these phrases — “I guess”, “then something happens”, “I forget lots of things”, “I don't know how to”, “why do I even have to”, “—k all this dumb s—”, “(swears)”.
The plus-err scale. Start at zero points, add one for each occurrence of these phrases — “This can't be right”, “This makes no sense”, “This is stupid”, “I don't understand why this doesn't work”, “This doesn't agree with the picture”, “This isn't asked in the problem”, “(sadface)”.
How many colors have been used? Two = plus one point. Three or more = minus one point per color over three. Zero = no points.
Does it take more than five seconds to find out whose paper this is? Minus five points. If identification is not possible, minus all the points.
Is there a picture? Plus two points. Is it a funny picture? Plus one more.
The weighted measure method. Get an accurate scale; the weight of the answers, minus the weight of the same number of sheets of answer paper, determines the grade. (Contributing factors: ink, sweat, blood, other byproducts of concentration.)
The curve measure method. For a rigorous empirical estimate of the answer, take the number of lines in it, divide it by the maximum of the same over all students, multiply by 100, and give that percentage of the maximum points for the problem.
The staircase method. Take all the papers. Throw 'em down stairs; the stair a paper ends on determines the grade. (The highest stair gets the highest grade, obviously, no matter whether the stairs go up or down. This was covered in elementary Newtonian physics, people. (Some math departments have actual numbered stairs for this purpose, though with the convenience of elevators they have become less common.))
Has the student uncovered the secret ink message hidden on the problem sheet, either using a lighter or his or her body heat? Yes? Then plus one point.