I attended an AP Chemistry short course offered by the College Board a couple of summers ago at Saint Joseph's College of Maine.  The instructor, Cheri Smith, from Yale Secondary School in British Columbia was phenomenal.  One of the things she shared with us was a Free Response question history (shown below).  I have been adding to it.  What is helpful is that the types of questions are defined, thus making it useful for predicting what the questions will be like on the new test.  No one really knows what they will ask for sure, but it is fun trying to guess and the students have fun trying to guess as well.  Not to mention getting them engaged.    

The yellow highlighted boxes indicate questions we have gone over.  Two different versions of the Free Response session are given.  This was started in 2002 as a result ______?  That is a question I ask my students.  Most of us in our forties did not have such things when we were young.

I have attached a link to where the Free Response History spreadsheet can be downloaded.  Feel free to use it and add to it.