It is probably handy to start out by outlining rank in the SCA. A useful approach is to start out with what you call a newcomer or someone of indeterminate rank (my lord) then go on to point out who the people with pointy hats are likely to be at the next feast.
A nice motto that you may wish to repeat is
Treat your lessers as your equals, treat your equals as your betters, treat your betters as your king and treat your king as God.It gets across the idea of how to treat all with courtesy in a stratified society.
Of course the SCA is not entirely any period in its titles and heirarchy (Lords outranked knights in medieval England) and it should be pointed out that this is one of the facets of the SCA that is done more for the atmosphere than to be authentic.
Whilst on the subject of inauthentic practices, the cloved lemon should be mentioned if it is used in your area. This SCA practice acutally has quite an interesting history.
Court should also be mentioned. Don't let them know how boring it is and they probably won't figure it out until they're sitting through their third or fourth. Believe it or not most people don't actually mind court when they first join because it is new and different. A particularly long court, however, may soon cure them of this. At any rate, it is worth pointing out that court is a time to be attentive and not for shouting out silly comments unless you know the person up the front and are comfortable that they would appreciate those comments. Also point out that court is there to recognise those who have done impressive feats, and is a good way of finding out who is doing what.
A small change of focus could be made so that you concentrate on what the awards mean, why they were created and so on.