Mathematics and General Aptitude are Queens of this carom. Get yourself as comfortable as you can and they will almost crack GATE for you. For Engineering Mathematics get Made Easy or Kanodia or Arihant book. Solve all the problems from the books. Take your favorite chapter. Start solving problems. If you get stuck on some points just note them down and move to next topic which is not related to that. At the end of your practice, take that paper on which you noted your mistakes and refer standard book to clear that concept.