There's not much time left to concentrate on a few particular topics because you never know what kind of questions will be asked, so it's better to start solving a lot of papers to get enough practice. The most important suggestion I can give is to make sure you revise your NCERT books as thoroughly and as frequently as possible, especially for Biology. For Physics and Chemistry, apart from studying NCERT texts, solve as many model papers and sample papers to get familiar with the concepts. The main thing to know is about the type of questions that will be asked and prepare accordingly. It will be a huge loss if you do not know the pattern of questions hence I would say it is best to go through the question papers of the last 5-6 years at least.