Here is some general advice that I have about both AP exams.
For teaching purposes or for job applications, I have taken portions of both exams and I personally have taught AP Chemistry for 4 years. My opinion of both exams is that they are very difficult. Please remember that you are receiving college credit for these exams if you get a score of 4 or 5 - most colleges want to be certain that you are knowledgeable about the information before they allow you to "skip" out of a basic course especially if you plan to major in chem or bio in that college.
In my opinion, the AP Biology exam is a reading comprehension exam - by that I mean that you will probably read somewhat lengthy passages, even in the multiple choice portion of the exam, and then be asked to answer questions about what you have read. You can expect graphs, tables and other visual formas of data. Here, is a question from the 2012 AP Biology exam that has been released by the College Board in 2012:
If I were answering these questions, I would read the prompt (beginning) of the question and then look at the data on the table and draw a quick conclusion or two. This question and its data is about respiration in crickets and mice. The respiration rates are at two different temperatures (10 and 25 oC). The numbers in the third column are also different.
Question 17 asks about the production of CO2 and O2 and is really a question about the experimental setup and your knowledge of the chemical equation that involves the usage of O2 - glucose + O2 --> CO2 + H2O - none of this information is explicit. Since a respirometer is measuring the volume of gas produced, it wouldnt be able to distinguish between O2 or CO2 gas. So, if you want to measure O2 consumption, your need to get rid of the produced CO2. How are you supposed to know this? Well, your teacher should have introduced the chemical reaction to you and s/he should of had you do an experiment involving a respirometer. If neither of these two things happened in your AP Bio course, then you will have to 1) ask your teacher for help, 2) learn information that was not explicitly taught to you and 3) practice, practice, practice so you get good at reading and answering the questions.
Question 18 asks you to infer the answer from the information given. If you read through the possible choices, you can eliminate choices B), C), and D) using common sense - for example, mice that had a lower metabolic rate wouldnt consume more O2 and if a mouse weighed less it does not make sense for that mouse to have highe O2 consumption. By process of elimination, choice A) is the only one that makes sense.
* sage means wise through reflection & experience