The best way is not to set any targets because when you do, you are limiting yourself to a certain extent. You may or may not achieve your target. But if you don’t set one, you can aim for the sky. AIIMS Delhi was the dream college of one of my friends who had literally no chance of making it into it. The only mantra he followed was not to expect yourself to perform to a particular or specific level, but rather give it your all. As for the preparation strategy, here is what he shared

• Practice Assertion Reason questions: This section is often underestimated when in reality it is a major rank-determining factor.
• Attend assertion reason questions in the beginning: Some might find it weird, but he chose to solve Assertion Reason before the exams as they required a fresh mind which would not have been possible after exams.
• Don’t forget the negative marks:  The negative marking might affect your overall performance drastically so beware of it.
• Always stay patient: Don't panic even if you find the question paper to be very challenging as you will forget whatever you have studied. 

Hope you score well!

Here are some tips that can help you prepare better AIIMS Delhi. 

• Physics - Follow NCERT books for Physics. Solve previous years' questions. The questions are not too difficult. Most MCQs are lengthy and calculative. Learn the shortcuts to solve questions. Solving JEE Mains questions can help. Electrodynamics, Magnetism, Modern Physics, EM, and Optics should be your main target.
• For Inorganic Chemistry, NCERT books are enough. Go through each and every detail thoroughly. For the Organic section, practice as much as you can. Physical section questions aren’t too difficult. If you have a good understanding of the basics, you can solve the questions easily. 
• For Biology, go through the NCERT books and coaching modules. It should be enough.
• The GK/logic section is easy. You don’t need to worry about it much.

Try to take a good number of mocks.