Go through the first 6 without timing yourself. Everytime you finish a test, go through the answers and write down all the questions you got wrong and try to understand where you went wrong. Use the last 5 tests to work on timing. Remeber to go through all the easy questions first and leave all the word problems till the very end. My biggest advise is DO NOT GET CAUGHT UP IN THE WORD PROBLEMS!!!! or else you will run out of time and only get through the first 20 questions.
Hope this helps.