Foam rolling is a great way to get a self massage and improve muscle flexibility by loosening tight areas and increasing blood flow. Foam rolling is a great preventative activity as well as a tool for recovery if you are injured. I try to foam roll after every run for about 5 minutes. I can definitely feel increased muscle tightness on the days I forget or when I don't have access to one.
If you are new to foam rolling, you will most likely benefit from using a smooth material such as this (which is what I started with many years ago). As you make foam rolling more of a habit and your muscles get more adapted, you can progress to a more rigid product with various surfaces such as this (which is what I have now and LOVE). If you are under 6 feet, the 12-13 inch size should suit you well. However, if you are over 6 feet tall, then I recommend a longer one (26+ inches).
Below are some of the top spots to focus on when using your foam rolling. I suggest about one minute at each area, but it can be less or more depending on the amount of stiffness you feel and if there are any knots you find. If there is an area that seems tighter, you will most likely benefit from doing several extra shorter rolls back and forth over that spot. One note of caution: Do NOT roll back and forth over boney areas such as the hip, knee, or ankle. Foam rolling is for muscles, not bones.
Quads: in a plank position, roll along the front of your thighs.
Iliotibial Band (ITB) and Vastus Lateralis (outer quads): in a side plank position or slightly tilted forward, roll along the outer parts of your thighs. You can come up to the front of the hip, but make sure you don't roll over your outer hip bone at the top. If it is too much force and weight on your lower thigh to have your legs stacked on top of each other, you can cross your top leg over onto the floor for more support and a less aggressive stretch.
Hamstrings: in a reverse plank, roll along the upper part of the back of your legs. For this one and the next one, I like to tilt my body side to side to get all angles of the muscles from the inside to the outside.
Calves: in a reverse plank, roll along the lower part of the back of your legs. As above, tilt your body side to side to get the inner and outer lower leg muscles as well. If you want to go deeper into the muscles, you can cross one leg on top of the other to give the leg underneath more pressure.
If foam rolling is initially slightly painful for you, no worries! It will get easier as your muscles become more flexible. Foam rolling is also a great core workout, as you have to hold yourself in a plank position most of the time.
Finally, it's a fun way to get some kisses from your dog. Have fun!