Buy a good AP chemistry preparatory book. This is not your textbook. This is usually a big (or medium-sized) paperback book that gives instructions, review and pointers about the AP exam.
Review the first chapters that discuss what the AP exam is, who makes it, who takes it, how it is scored and whatever other information it tells you about the exam. So, read the material and take the diagnostic test. Then go to the AP website and any other related websites.
Read, study, underline and highlight the chapters on the Basics and on Stoichiometry. Do all these things before your first day of class in the fall.
Memorize before the first day of class the following: the solubility rules, rules for naming ionic compounds, rules for naming acids, determining oxidation numbers, variable valences for transition metals and polyatomic ions. There's not a lot of memorization in chemistry, but these are pretty important.
Go to the front of your AP Chemistry prep book and find the schedule set up for getting ready for the AP exam. Determine which schedule is the best fit for you. There probably will be one for all year, a semester-long schedule, and a shorter one for six to eight weeks.
Start reading the review chapters and taking practice tests. Stick to one of the review schedules, unless the time is so short you need to set it for two or three weeks. It's better to plan ahead.