Hello,

If you want to start your preparations from class 11 then you may follow these steps: -

1. Be properly updated regarding the syllabus
2. Start preparing according to the syllabus
3. Right down topics or subjects that you think you are weaker among all others and start with them first.
4. Make a proper time table
5. If you can buy preparation books and do so that will help you in your preparation.
6. Solve previous papers ( You can get them in the preparation books).
7. Be thorough with you course books like mathematics, physics, chemistry, etc.

Hope this helps. All the best

Just started from today and focus on ncert maths as well and miscellaneous exercise is compulsory as sometimes it may be seen that upsc(who conducts nda) asks direct questions from miscellaneous of ncert.

and if you want to get your prepration more competative than i suggest you a book THE PATHFINDER from arihant publication.

ALL THE BEST