How can you keep from getting blue balls?

The only way to effectively prevent blue balls is to finish. Either have your girlfriend finish you, or get yourself off. It is easier if she does it, as it makes the act seem less of an issue, and that she enjoys helping you out. Some girls enjoy seeing and helping their man finish while others dislike the act, probably due to the fact that some of the cum gets on her hands. If you are not using a condom, paper towels work well to finish into. She can wipe off her hands afterward, and then the towel can be thrown away or flushed depending on type.