The ramblings below are meant to provide some guidelines to those who are new to taking graduate level marketing or management exams. These are my own ideas only, and might not necessarily reflect the way that other professors look at your work.
Issues of sentence structure, grammar, etc. DO count. Outline/list only when appropriate. Use traditional length paragraphs (around five sentences) - single-sentence and two-page paragraphs are very difficult to read and interpret. If English is a second language and you believe that your writing is not specific enough, comment in parentheses in your native language - this can be interpreted/negotiated after the exam. In discussing product diffusion, one of my students drew a picture of a Victrola when he couldn't recall the word "phonograph"; he ended up with very high marks on his exam.
One exception to the above is when you are running out of time. It is better to receive a mediocre mark due to form than a low mark for lack of an answer. An outline helps you to pace your writing and to judge your distance: you should not run out of time if you plan ahead by sketching a few outlines first. A statement attributed to Abe Lincoln is very relevant here: If you have six hours to cut down a tree, spend the first four sharpening your axe. A rule of thumb is that most people will write about three to four pages per hour on a "blue-book" exam. If you are writing at a pace of more than four pages, you are probably rambling and not doing enough thinking and planning. If you are writing less than three pages, your answers are probably not complete in coverage.
Note also that penmanship is important. Someone must be able to read your writing to be able to score it. If the person scoring your answer has difficulty in reading or interpreting what you have written, they won't take the time to attempt to figure it out. It is your responsibility to provide evidence of what you know and not the responsibility of the scorer to find that evidence. Although your answer should be structured in sentence-paragraph form, do use tables or pictures if these better show relationships than could be done in sentences.
"Do you agree or disagree with this statement" is not meant to elicit a simple "yes" or "no" answer. You are being asked to contrast and discuss the conditions under which the statement is true and is not true, to contrast points of view of different scholars, to contrast various ways that the issues of the question could be interpreted, etc. Requests such as "comment", "assess", or "discuss" generally imply the same. Such questions are designed to provide you with the opportunity to demonstrate your depth of understanding of and insight into an issue.
"Depth of understanding", however, does not suggest that you should attempt to write everything that you know about some topic. Do not stray from the issue of the question in an effort to show how much you have learned. Be sure that what ever you write is relevant to the question. (Recall: outlining is a necessary step.) Be very careful not to spoil your answer with statements that clearly show what you don't know! Like generations of professors before me, "I'll give you all the rope you need to hang yourself." Use only what you need and use that wisely.
Always be careful that the reader will be able to understand your perspective or context. Do not assume, for example, that the reader was exposed to the same examples that you recall from some past discussion in a class. Importantly, do not assume a local or North American environment without specifically stating this assumption. Foreign students with a North American professor can sometimes put themselves at an advantage by assuming an environment (if appropriate) with which they are familiar and which the professor is unfamiliar.
"If you can't dazzle 'em with brilliance, baffle 'em with bull" is not to be attempted, however. You must support every assertion that you make. Balance this support with evidence from real-world cases and with the writings of scholars in the discipline. No matter what you say, a professor can almost always find a statement to the contrary that was made by a scholar or executive who is more credible and famous than you. Avoid any statements that sound like personal opinions without substantiation. Any question which asks for an opinion is a trap!