1. Familiarize with the format and content of the GMAT math.
The GMAT quantitative section has around 24 questions in Problem Solving (PS) and around 13 questions in Data Sufficiency (DS). For both types, you will pick your answer from 5 choices. These will be problems in algebra, geometry, and general arithmetic. The PS questions are quite straightforward, albeit confusingly worded. The DS is uniquely a GMAT feature and it is something you learn about exclusively during the GMAT preparation.
2. Simulate the actual GMAT math.
Simulate the real GMAT math as realistically as possible during practice. In the later part of your review, try sitting through 37 questions in one stretch of 75 minutes. Have access to a computer adaptive test and sit through one at the start of your review. This will give you an idea of how much preparation you need. Try again in the middle of your review period and near the end to measure how you have improved.
3. During practice tests, do not use a calculator.
You will not be allowed to use a calculator during the real test, so practice and develop the habit of solving problems without one.
4. Work against a clock.
A correctly answered question will have no significant contribution to your GMAT math score if it took you 5 minutes to solve. In the real test, you only have 2 minutes maximum to solve a question. Going beyond that is like stealing from the time allotted for other questions. When starting out (say, first month of review), you may allow longer time per question. The focus here is to study content and methods. After that, shorten the time until you approach the 2-minute limit. Continue focus on content and methods but, this time, becoming more time-efficient.
5. Develop shortcuts and calculation techniques.
Avoid meticulous calculations. For example, use π = 22/7 instead of π = 3.1416. It is much friendlier to manual calculation. Be familiar with values of common fractions, percentages, and square roots. If you know that the decimal 0.6666667 equals 2/3, using 2/3 is easier to manipulate in an equation.
6. Practice on a scrap paper.
In the actual test, you will be provided with scrap paper. Develop the habit of writing the steps in solving problems. Other GMAT aspirants are concerned that writing will consume time. On the contrary, writing allows you to comprehend the question more clearly and clarifies all useful data given. You will then have a higher probability of arriving at the correct answer in the first try. Errors are also easier to spot when you will do a review of the answer.
7. Remember that graphs and charts can be visually analyzed.
GMAT math questions using graphs, tables, and charts can usually be analyzed with your ability to interpret them. Save time by being familiar with axes, legends, units representing data, and the structure of different types of graphs (bar, circle, line). The content of this type of problem does not entail complicated math and answers can be derived from studying and interpreting the illustrations.
8. Geometry problems are not always drawn to scale.
As opposed to the graphs and charts, do not assume that geometric shapes are drawn to scale unless the problem specifically states so. Solve problems based on your knowledge on geometric principles.
9. Memorize the 5 answer choices for DS questions.
Treat each of the statements independently. Ask whether the statement is sufficient to solve the question asked in the problem. If you are sure about the sufficiency or insufficiency of at least one sentence, you can eliminate 2 to 3 choices. That narrows down the probable answers to 2 or 3 instead of 5.
