Most Math problems that I have seen can be broken down into smaller steps, some steps which are obvious and some others not so obvious. Solving the easier steps can give us clues to how we can solve the difficult steps in the problem. Also, if we are attempting an exam with multiple questions, developing the intuition to decide which problems are easy and which problems will require more time is important. Also, applying common sense always helps. If you are given the choice to come back to a problem, don't let your ego get you on spending too much time on 1 hard problem. Solve everything which is obvious and then come back to the harder problems at the end.