Japan is a culture of bows (お辞儀) for every occasion. I will be exploring those moments and the proper etiquette for bowing over the course of several weeks.
Posture Men - hands at the sides Women - hands at the sides or clasped in front
Movement Keep your eyes down Keep your back straight Bend at the waist
Strategy Bows of apology are the longest in Japanese culture; just as the langugage has you lowering yourself in the eyes of your observer, so do bows, only literally so.
Bow first. Start apologizing. Continue bowing. Bows of apology usually have you bending your back at a 45 degree angle, especially if you're dealing with a superior. The duration of the bow is important as well; usually three seconds is sufficient, but you should weigh your actions based on the offense.
If you happen to be off your feet during a bow, on a tatami mat, it is proper to bow kneeling, with your forehead touching the ground. This is referred to as saikeirei (最敬礼), the most respectful bow.
Unlike in greeting situations, where one speaker will bow a little too far, causing the observer to bow slightly less, and each follow in a series of progressively smaller bows, an apology is for you alone. Make it count - angle, frequency, and duration.