How do I go about it? Sitting next to your partner, take his right hand in your left hand, and position your right hand on his wrist, with your fingers pointing towards his shoulder. Gently go from the wrist to the elbow, then continue up to the shoulder, before going back down the length of the arm. Do this twice.
Next, place your two hands parallel on his forearm and go up to his shoulder, applying even pressure. Go back down, releasing the pressure. Repeat this several times. Finally, hold his right hand between your hands and use your thumbs to make kneading movements on his palm, then slide your index finger between his fingers. Repeat with his left arm.
Why is it so good? We often ignore them, but the arms contain many erogenous zones, notably the elbows (at the crook), the wrists and the hands. Very rarely caressed on a daily basis (especially the hands!), the hands are particularly sensitive to massage, which provides intense sensations.
A good time to try it: When you feel like you're in a routine between the sheets and daily physical contact is rare. Massaging the arms lets you rediscover and focus on your partner's hands and shoulders, parts of the body which we all to often neglect.
An extra idea: To spice up the massage a bit, slip your tongue between your partner's fingers and gently kiss his fingertips.
Note: Because of their symbolic meaning (they protect and coax), erotic massage of the hands and arms reinforces your feelings for each other and forges stronger links between you.