If you want to finish your degree in four years, you will probably need to take a few summer courses.   There are differences between summer courses and regular courses.

Note that my university is small.  Classes are small; therefore, summer classes are even smaller.

Short Time Period

Summer classes do not last as long.  So you will be going through the material a lot quicker.  That is why it is sometimes better to save your easy courses for summer.  Good luck taking Calculus II over the summer.  Psychology 101 seems a lot easier.

Classes are more relaxed.

During the summer, professors seem to be more laid back.  Especially if the it is a small class.  Small classes tend to become more discussion type courses than lectures, which to me is always a bonus.

Picking Summer Courses

I have two perspectives on this.  One was mentioned above; take easy courses.  My other view is to take a course that will challenge you and that you will enjoy.  If you are a computer science major maybe take the course on artificial intelligence and really dive into it.  If it’s the only course you are taking you should be able to really focus on the course, and you will come out of it being a lot better in your field.