Saying thank you
I once read in some parenting book that you shouldn't thank your kids for doing what is reasonably expected. But that never sat well with me.
When my grade schoolers do things like clear the table or hand me the remote control or turn the sound down on the TV. I usually say thanks--just because it feels right.
Though my kids are still young, I am fairly satisifed with their response to little favors I do for them. They usually thank me, though sometimes they need to be reminded :)