First of all, never think of HOW.
Just start doing it with patience. One must know his/her strengths and weakness so work according to that. Focus on subjects which you find difficult but remember never neglect other subjects.
I advise not to take any coaching because
- Requires times on travelling.
- Hectic schedule after attending the school.
- No time for self study.
- Sometimes you get in wrong company of non serious students.
- Exhausted after returning from coachings.