How to bow
I work at a medical clinic in Japan, and had to participate last month in an etiquette workshop in which we learned how to bow properly. Although I'm no expert myself, this is what we learned:
1. You should face the person to whom you're bowing. There are 3 kinds of bows: #1-casual bow that consists of nodding the head, used for coworkers and friends, #2- regular bow that consists of bending at the waist, #3- deep bow for formal occassions.
2. For the #2 bow, bend at your waist to about a 45 degree angle, hold for a couple of seconds. Your back should be straight. Instead of looking at your feet, you should look about 2 meters ahead of you; this ensures that the line from your head to your waist stays straight.
3. Your hands should be crossed at the area just below your navel; your left hand should cover the right hand. Make sure your elbows are bent slightly.
4. For the #3 bow, bend a little more deeply (maybe 60-70 degrees), and hold for slightly longer.
If you are sitting on tatami mats when bowing, you should sit with your legs folded under you; place your hands on the mat in front of you with your left hand on top; bow until your head nearly touches your hands.