1. First and foremost keep with yourself last year's question papers (available easily on BHU's website) of not only Maths group(whole paper) but Bio group too(only the Physics and Chemistry part of it) because there is a tendency of repeating questions or following the existing trend of questions.You’ll get a basic idea of what chapters to stress on.
2. The questions aren't that hard. The type can be broken down into 10%easy ,which almost any one can get right,60%average - for which you just have to know the right concept do the right mathematics and figure out the answer and the rest 30% is tough ; to the extent of above average questions in JEE mains.(don't worry about it because you've already garnered enough marks to get through)
3. Third is time management during the exam. While the questions being relatively average, the given time(150 minutes) seems short. To overcome this problem start your preparation for the exam and solving the question paper with Chemistry because they are the easiest among the three sections and take very less time.Then go on to Physics and Mathematics. Do not give undue importance to the questions you don't know the answer to. Try to score atleast 100(out of 150) in the Chemistry section.
4. Your focus on class 11th and 12th syllabus should be 40/60.

The cutoff for general candidates is around 190–200. So try to score 240+