Tenth: leave out cleaning supplies and spare sheets. Trust me on this one, it's really easy to forget rule the first when you "can't find" the bleach.
Eleventh: do not think about going home until 12:01 PM Sunday. Seriously, everything will more or less be like you left it back at your place.
Twelth: have a contract. Worrying about your place will take 94% of the fun out of this escapade (eHow has some info on drafting up a lease agreement).
Happy house-swapping. Next time a free and fun idea for people just dating.
*Note: The Media calls articles with tangible "try this" takeaways "service pieces." Only in America!
**Note: If anyone has kids, their room(s) is (are) totally and absolutely barred from any entry.