GMAT is a time bound standardized test to evaluate your managerial skills. It’s not so much about knowledge (advance knowledge of concepts is not required), as about familiarity with and the mastery of a particular way of reasoning. The mantra to get good score is “get the answer in minimum time and with minimum effort”. To do so :
1. Work with optimum information. A cluttered mind will adversely affect your performance. Learn to distinguish between optimum information and information overload. Avoid the in depth information about the concepts that most sources provide.
2. Get familiar with and master the type of reasoning that GMAT employs. For this, a regular practice followed by in depth analysis and a revision is required.
Never practice more than 20 questions from each section (It’s not about how many questions you practice but about how you practice and what you learn from every practice session).
In the correct questions, analyze to determine whether your approach can be improved. In the wrong ones, never seek your answer from other sources. Instead compare the right option to the wrong ones and find the point of difference between the right and the wrong to understand what makes one correct and other wrong. Determine what line of reasoning made you choose the wrong answer, work on that reasoning and then revisit the question with the correct reasoning.
3. Base your approach on process of elimination.