how to prepare well for any MBA exam?

There are quite a few entrance examinations for MBA:

CAT: CAT is an online examination of 3 hours duration. To be eligible for CAT, you should have completed your Bachelor's degree in any discipline with a minimum aggregate of 50%. It is 50% for General Category and 45% for Reserved Categories.
MAT: To be eligible for MAT, you should have completed your Bachelor's degree in any discipline. There is no minimum aggregate criteria.
IIFT: To be eligible for IIFT, you should have completed your Bachelor's degree in any discipline with a minimum aggregate of 50%. It is 50% for General Category and 45% for Reserved Categories.
SNAP: To be eligible for SNAP, you should have completed your Bachelor's degree in any discipline with a minimum aggregate of 50%. It is 50% for General Category and 45% for Reserved Categories.
NMAT: To be eligible for NMAT, you should have completed your Bachelor's degree in any discipline with a minimum aggregate of 50%. Candidates with a minimum of 2 years work experience are preferred.
CMAT: To be eligible for CMAT, you should have completed your Bachelor's degree in any discipline. There is no minimum aggregate criteria.
You can check the complete list at our page:https://bschool.careers360.com/articles/top-mba-entrance-exams-you-must-take
The syllabus more or less depends on the topics like:
Quantitative Ability
Verbal Ability and Reading Comprehension
Data Interpretation and Logical Reasoning

QA can be categorised into Arithmetic, Algebra, Geometry and Advanced Mathematics. Practise chapter by chapter and develop mental calculations. Like practise more of basic summation, subtraction, fractions and tables. Numbers, Percentage, Profit and Loss, Simple and Compound Interest, Ratio, Proportionality, Time-Distance, Time-Work, Mixtures, Averages, Partnership, Permutation and Combinations, Probability, Set Theory, Progression and Series, Line, Angles, Triangles, Quadrilaterals, Polygon, Circles, Ares, Volume, Height and Distance, Coordinate Geometry, Basic Trigonometry are few important topics.

Because this section involves mathematics and takes most of your time, your focus should be on solving the problems efficiently in the beginning. Even if it takes time, practise upto perfection. Practise as many questions as you can in the conventional way. As and when you get a grip on the subject, you can go for short cuts. Memorise tables, square roots, cube roots, conversion from percent to fraction, etc. Solve sample papers on Mathematics. In the beginning, do not worry about the time it takes. As you practise, you will get the hang of the subject and it will be easier for you.

In Verbal Ability session, command on your English, Grammar, Vocabulary, Understanding of the given paragraph are of more importance. Reading English NewsPaper will also help you in your preparation.

Read articles from time to time. Follow newspapers, magazines, and watch the news channels and browse the internet to keep yourself updated. You will need a lot of reading to help you in the comprehension section. You will need speed to help you in this section and you can achieve that only by thorough practise and reading. Take time to understand the question because most answers are interlinked

Data Interpretation and Logical Reasoning needs to be practised as much as possible. Comparison of data, Data Analysis, taking clues, interpreting missing data, coming to conclusions and making future projections will be covered under this Category. The questions here are interlinked and so if you get one formula correct, cracking the next few questions will be easy. So it's important to memorise and practise formulae. You should cover topics like Data tables, Data Charts, Bar Diagrams, Pie Charts, Graphs, Data Comparison and Analysis.

As this is the most tricky section, this needs a lot of practise. Solve as many sample papers as possible to get the hang of the section. Make notes when required. Regular practise can help you understand and solve the questions easily as time goes on.

Overall,once you know the syllabus, it's easier from there on.Go through the previous papers to analyse and prepare a comprehensive plan and set priorities according to the importance of different topics across sections. Customise your own study plan based on your strengths and weaknesses. Gauge your preparation from time to time by taking mock tests. Solve questions to check your levels of preparation but not to set any targets. Remember, its ok to have cheat days and relax. But make sure you have a plan and stick to it for the next few months.