Solve only one problem at a time, writing down what is being considered. Let the problem solve itself. Begin by writing down what is sought. Write what you know, then what you believe to be the right solution procedure, as well as known facts and possibly true relationships. Study a short, meaningful amount of material at one time, with intense effort.
Concentration is essential.
Begin each study session with a short review. Take frequent breaks. Keep tight control on your focus. That is, don't allow yourself to become confused at any moment of studying as to what you are actually trying to accomplish. Work slowly and surely.