Concentrate on the subjects you are weak in or which seem difficult. But also don't neglect other subjects entirely but keep your prime focus on subjects like science, maths, accounts, economics.
Try and create a schedule to develop the habits of studying and try different techniques of memorising and comprehending the concepts. Must use NCERT and practice questions from previous year board papers and sample papers.
You should avoid taking stress and practice each and every day. Maintain a schedule where you can also relax a bit so that you have your recreational time too.