Once I started running, and especially once I started having trouble with my knees, I had countless people tell me I should get a foam roller. I admit I was a bit naive and had rarely ever heard of anyone using such a thing prior to about six months ago. Before I started running in September 2013, I only rode my bike for exercise and never felt the need for a foam roller. My whole life I've avoided the gym so useful tools, like a foam roller, rarely, if ever, crossed my path.
When I started having stiffness and some swelling in my knees, my wife went out and bought me one of these from the Running Room last October. At first, I thought $30 was a lot for a piece of foam. But it is $30 well spent. Countless friends and acquaintances of mine that are far more fitness educated than me swear by their foam rollers. A co-worker of mine big into heavy weights swears by his foam roller before and after every workout.
First, let me warn anyone who has never used a foam roller before, this is going to hurt. If it makes you cry, you're doing it right. After a bit of time with it though, the pain becomes far more soothing than painful. The instructions are simple. Basically, prop your legs on the foam roller and hold up your upper body with your elbows, arms, or hands. Then roll back and forth from near your hip down to near your knees.
I usually start with my quadriceps (front), then iliotibial band (outside), then hamstrings (back), and lastly adductors (insides). This routine just works for me. I try to isolate each leg by itself. And the key is that when you find a sore spot, go over it again and again to work out the soreness. I often find that the sorest spots are somewhere in between the muscles, so I end up on a 45 degree angle targeting somewhere in between my quadriceps and iliotibial band.
After a solid ten minutes, my legs are often much more relaxed and the stiffness is almost completely dissipated. In all honesty, the pain is much more relief than actual hurt. Yes, it hurts. But it is a soothing pain. And it will feel better once you're done anyway.
I'm not about to make a video doing this myself, so if you want more of a visualization, check out this how-to from Runner's World.