Foam roller is a great tool to warm up before working out and cool down to release myofascial trigger points after workout. It aids in stretching the fascia and promotes normal range of motion as well as muscle recovery. To release the trigger points in a muscle, you roll on a roller and stop on points that are painful and refer pain into other areas or locally. Working on tight muscles will cause some discomfort and pain, but it should be tolerable. The release of trigger points restores normal muscle movement and decreases pain. By using foam roller, you increase circulation to the muscles.
How to foam roll?
Apply moderate pressure to specific muscle/muscle group using your bodyweight. Roll slowly about inch per second. Once you find a painful spot, stop and hold position for 30 seconds. Relax as much possible. The pain should be decreasing as you hold on a spot. If the direct pressure is too painful, work on areas around it to release it first and come back to painful spot, after other tissue around has been released. Do not roll on a joint or bone.
Feeling sore the next day is normal. Drink lots of water to flush out any muscle metabolites and lactic acid. If you are sore next day wait 24-48 hours before working on the same area.