Do Kegel exercises
Both men and women can improve their sexual fitness by exercising their pelvic floor muscles. To do these exercises, tighten the muscle you would use if you were trying to stop urine in midstream. Hold the contraction for two or three seconds, then release. Repeat 10 times. Try to do five sets a day. These exercises can be done anywhere—while driving, sitting at your desk, or standing in a checkout line. At home, women may use vaginal weights to add muscle resistance. Talk to your doctor or a sex therapist about where to get these and how to use them.
Found on: http://www.helpguide.org/