Starting with my daughter, who is now 25, and with my stepkids, who are 11 and 14, I make sure that they thank service people in uniform. When we are in a store, I always make sure they stop, thank them and shake their hand. Now, they do it without me even asking. When they've asked me why, I've always said the same thing: "You are free because of them, and you never know if they were a prisoner of war or someone who was once missing in action." That gives them the chills and then thanking them is easy.
It should be even easier to remember today (Sept.18) -- it's National POW/MIA day!