Learning is a constant process of integrating new material into old, and revising how you view some part of the world. If you are having trouble understanding a concept, find another textbook and read the corresponding section to see if it is clearer to you there. Develop your problem-solving skills. This will involve general thinking and reasoning skills as well as mathematical and symbolic reasoning and logic. Sharpen your basic mathematical skills so that they are second nature to you.
Most students have at least a basic knowledge of the concepts needed.
Learn how to use your calculator effectively. If your calculator has lots of buttons whose purpose is unknown to you, this is of limited value. Learn and practice using units for physical quantities. These can be of immense help in setting up and checking mathematical procedures. Check every answer for mathematical and physical reasonableness.