Summer is the perfect time to spend reviewing material from old courses in preparation for the new ones that you will be taking in the Fall semester. To prepare for my next level of Physics I have been reviewing physics 1, this has actually been really helpful to me because I understand a lot more of the basic materials then I did before.The Physics 1 for Dummies book has actually been a great study resource as well, I suggest maybe using a book like this one for review, it is not as concentrated as the text used in the course so it is a little more easy to pick up the concepts.
Another thing that many cadets do over summer is study for the AFOQT, or the Air Force Officer Qualifying Test. This is a test that depending on whether you pass or fail, allows you to continue in the AFROTC program and hopefully commission as an officer in the US Air Force. So as you might have guessed, this is is exactly what I am doing.
I also have a for Dummies book to study for the exam, I honestly prefer the for Dummies books because they have so much good information in them and they are written by people who have actually taken the exams or courses.So the authors really know their stuff and they know how to present it in a light that interests the reader and aids in the development of their knowledge in that field.
I urge you to please spend at least an hour a day reviewing topics that you are not entirely comfortable with. This can really give you the upper hand in your studies as in college all the courses you take have aspects in them that you will continually use throughout your college career and perhaps beyond.