As soon as they learn to speak!! Hearing cank gu- from a toddler is wonderful. my kids were also taught to send thank you card! They are adults and still send them. when neices and nephews were small i would send a gift but required a thank you note! If you couldn't write- draw me a picture! Now, nothing! Sad but then their parents rarely acknowledge gifts so... i rarely send them gifts anymore!!i sent everyone quilts for Christmas- only my mom called to say thank you!! Sad.... manner are forgotten! No please, thank you, excuse me, yes ma'am, no sir instead of huh, what?? Those of you in 50's or more- how many young people hold doors open for you???