Well, here's an approach.
Step 1: Attempt a past paper with no restrictions on time. Circle any questions you cannot do (surely you can do the first quarter without any problems; if you can't, then you probably do not have a strong grasp on fundamental concepts).
Step 2: DO NOT LOOK AT ANSWERS - instead, turn to any resources you may have containing the relevant information (especially internet tutorials on how to solve particular problems)
Step 3: Re-attempt the question showing FULL WORKING (do not neglect this...) and check answers.
Note: If you cannot answer the question after your attempted re-try, then ask a teacher/tutor or friends
Step 4: Repeat for another paper
The sad truth is, you MUST do papers. Textbooks often divide topics and do not provide "examination style" questions - i.e. they suck. And don't bother doing the 'easy' questions, just do the last few.