How do you relieve muscle cramps after exercising?

Appropriate cooldown. Always cool down after working out. Don't sit; walk around and keep your muscles moving as they cool off. Stretch thoroughly, slowly, and gently. After you have cooled down, you can use cold heat rubs, massages, and hot tubs to try to minimize soreness and cramping.
Stretch & heat. Stretch the muscles and the use heat to relax the muscles and help get increase blood to them.