Develop a study plan well in advance:
Start preparation for the exam at least 6 months in advance to get a good grip on the syllabus
Work on all the test sections and plan them according to your strengths:
The sections include Analytical Writing Assessment (AWA), Integrated Reasoning (IR), Quantitative Reasoning (QR) and Verbal Reasoning (VR). Focus on your strengths and prepare for the weaker sections with greater effort.
Choose your prep material wisely
Using effective prep material can give you an edge in the examination. Using GMAT official prep would be great place to start
4.Start managing time wrt the exam asap
The development of time management skills can take one a long way in GMAT. Start timing question solving as soon as possible and build a habit to solve questions in given time frames.