The Body Scan is the first practice introduced in Mindfulness-Based Stress Reduction. It supports increased awareness of the body and integration of body and mind. The Body Scan is also a great way to start working with mindfulness of attention. Finally, the Body Scan is usually a relaxing experience (but not always!).
Best done with verbal guidance, the Body Scan is usually done lying down on your back. Find a comfortable, quiet place to lie down. Reclining in a comfortable chair is an option. Bed can too comfortable and you fall sleep. Jon Kabat-Zinn's line about falling asleep during the Body Scan is that our goal is actually to "fall awake"! However if the Body Scan helps to ameliorate sleeping problems, so much the better.
Starting with the toes we systematically "listen to sensation" - just noting sensation in areas of the body moving slowly up from the toes to the top of the head. If the attention wanders (and it will!), gently bring it back to the current area of the body. Short body scans can be done without listening to verbal instructions for for the full 30-40 minute practice, listening to the audio is essential.
Read a full description of the Body Scan practice by Jon Kabat-Zinn from his book Coming To Your Senses: On The Body Scan
Below are some recordings currently available through Mindfulness Northwest. Googling on "body scan" will find many more.