Last Saturday, MissK presented "The Voodo That You Do," a class on D/s rituals. She said that one critical element of a ritual is that it must be enforced, otherwise its a service or a habit.
For example, if your submissive always calls you "Sir," that is a sign of respect. If he/she is punished for failing to call you "Sir," that is a ritual.
The other requirement is that the action must be meaningful to both parties. It does not have to be meaningful to the rest of the world, but it must mean something to both of you.
She presented numerous examples of ritualized forms of address, greetings, table manners (like not eating/drinking until signaled), posture and positioning, etc.
The combination of meaningfulness and the mindfulness that the posibility of punishment brings are a powerful force in maintaining a D/s state of mind, anywhere from an undercurrent that only you feel all the way to full-bore 24/7 servitude.
A warning to Dominants, however, is that ignoring an established ritual is not just a missed opportunity to add something to the relationship; it is an active negative, because you are blowing off something meaningful.
MissK's presentation was excellent, and we're going to have her back soon to present it again--Saturday's class was about half sized, with only about 20-25 people (lots went to RenFaire) and we thought it should be heard by more.
Clay