You should get into the habit of examining your testicles. Just as some people should practice breast self-examination each month, people can practice preventative medicine by doing testicular self-examination.
The best time to examine your testicles is right after a hot bath or shower when the skin of the scrotum is most relaxed. Each testicle should be examined with both hands by gently rolling them between your thumb and fingers. (see diagram)
Learn to recognize the epididymis by its spongier texture. The epididymis is located along the rear border of the testicle and should not be mistaken for an abnormality.
If you discover any lumps or growths, or if the testicles are swollen, you should see an urologist immediately.