Secure the mic pack to the actor's body. Female actors can place the pack in her bra. Those of either sex can use a bandage to secure the mic or place the pack in a pocket.
Thread the microphone cord up the actor's back and into his hair or through his side burns. Secure with a bobby pin or hair clip. You can also place the microphone over the ear and onto the face, but this is usually more noticeable.
Place the mic cord on the face. Experiment with different placement to ensure the best sound quality. When you're satisfied, use clear hypoallergenic surgical tape to place it on the actor's cheek.
Cover the microphone cord with moleskin, if you feel it can still be seen. This will further help it blend into the actor's skin, although it will be noticeable up close. Those sitting away from the actor will likely not notice it.