1. NMAT is a speed test. To get into Narsee Monjee, you need to attempt 80-90 around questions out of 120 questions - and that too in 120 minutes!
2. NMAT level is slightly on the lower side when it comes to the difficulty of questions. Focus on building speed and accuracy and NM can be cracked.
3. Some topics to specially focus on:- <Assuming you are already preparing for CAT>
3.1) Percentage, Average, Tabular DI, Bar graph, Line Chart, Pie Chart and Interests.
3.2) Data Sufficiency, Assumptions-Reasoning-Inference-Conclusion based non verbal reasoning, Matrix Formation, Cubes-calendars-clocks.
3.3) HCF-LCM, Cyclicity-last digit and factorials, Number classification, Factors and special numbers like prime numbers, perfect numbers. Number series basics and odd even numbers.
3.4) Para Jumbles, Antonyms, Synonyms and Fill in the blanks(word usage), basic preposition-tense-article-SVA based error spotting.
*Other topics are also important, but focus more on these. Spending more than 60% time on these topics is a wise idea.
4) Section cut off matters - so make sure you solve with confidence and choose single type questions more when the sectional time is running out. Solving set based questions is not cool when you have scarcity of time.
So final words:
Focus on speed. Practice 2-4 NMAT mocks/previous year papers. Also try solving 2-3 previous year MAT papers and if possible 2-3 IBPS PT papers in time limit. This will help you build the necessary knack to thing NM :) Also, make sure you do a very strong analysis of the papers after solving them in time limit. Understand it is very important to avoid silly mistakes as well.
Passages in NMAT are easy to moderate normally. So, not much here. Query based and direct logic based practice and 1 hour reading daily of The Hindu or of relevant topics like philosophy, sociology, psychology, economics etc. should be done regularly 10 days before the exam to tune your mind for the final hit! Also revise whatever words you have learnt till now - list/usage whatever way!
All the best!
Alumnus, IIM Ahmedabad