The top entrance exams after Class 12 in India depend entirely on the field you want, so the smart move is to choose exams based on your target course, not to attempt everything.
For engineering, the main exams are JEE Main and JEE Advanced, along with BITSAT and various state level exams. For medicine and allied fields, NEET is the single national exam.
For general degrees at central universities, CUET has become the main gateway, covering courses across arts, science, and commerce. For law, the key exams are CLAT and AILET, and for design there are NID, NIFT, and UCEED.
Other important routes include NDA for the defence forces, hotel management entrance exams, and specific university tests. Commerce students often move towards professional courses like CA, CS, and CMA, which have their own entry exams.
The key is to work backwards from the career you want. Decide the course, then find the exam that leads to it, and focus your energy there.
Example: A student who knew she wanted a central university degree focused only on CUET instead of scattering her effort across five unrelated exams, and got into her first choice.
One practical tip: Do not attempt every exam you hear about. Pick one or two that lead to the course you actually want, and prepare for those properly.