All you really need to know to give a decent massage is where the nerves and muscles are bundled, since that's where circulation tends to block up. My go-to is under the shoulder blades, lower back muscles, the back of the legs, the scalp, the palms, and feet.
From there, you just knead it to help it relax. Knots in the muscles are just stiff muscles, so find particularly firm spots and rub them perpendicularly to relax them and release that energy. The strength depends on a person's preference and condition. You can try rubbing with your fingers, your entire palm, your elbow if you're smaller than them, or your knuckles.
Be sure to communicate plenty to get feedback for adjustments.