Be sure to attend all discussion and review sessions with the TA, and be prepared to ask questions about aspects you do not understand. Working in small groups can be an effective way to tackle problem sets - but only if every group member actively participates. Note that almost all TA's hold office hours and they will be happy to work with you. In more advanced classes, problems should be discussed with the TA and then with the instructor. In your university science courses you will be asked not simply to remember information, but to use new information and new experimental tools in problem solving and analytical tasks.
Some students find that they have difficulty scoring well on an exam that requires problem solving.
Scan the test at the start. Do the easy questions first. Write down something for every question, even if just to indicate the line of reasoning one would pursue. Read the question carefully. After you have completed your answer, go back and read the question again to be sure that you have covered all components requested.