The difficulty level of the NISM exams ranges between average to moderately high. For some exams, the contents and way of testing could be more complicated than the others. 

• The NISM Investment Advisor Exams (Level 1 and 2) contain more practicals as compared to the other courses. 
• On the other hand, exams like the NISM (Series VI) Depository Operations Certification Examination contain a very high share of theory portion in their syllabus.

To pass a module, you need to secure a minimum of 60% in most of the module exams. Also the exams come with a negative marking of 25% per question. 

Very few exams like NISM (Series VA) Mutual Funds Distributors Certification Examination have a minimum passing marks criteria of 50% and they do not have any negative marking.

You can take the help of test prep training for practice papers as they will provide you with good resources.