I thought that teaching manners to kids would begin when they were just wee little babes, looking up with adoring eyes as you remind them to say "Please!" when they ask for a sippy cup of juice and really be ironed out by the time they're, say, eight and eleven. (I just randomly threw those ages out there. It's pure coincidence that that happens to be the ages of my children. I promise.) I'm realizing, however, that teaching manners is an ongoing thing, as I constantly remind them to speak politely and hold open doors for people and things like that. I'm afraid that this may well extend into their adulthood.
One of my favorite lines from "Despicable Me" is where Gru says, in response to a "pretty please" from one of the girls, "The physical appearance of the please makes no difference." (This line is made even better if you say it in your head with a Russian-esque, Gru-like accent.)
I heartily dislike it when my kids (or anyone's kids, for that matter) say, "Get me a drink, please!" and I'm very likely to respond with, "The physical appearance of the please does not make that statement polite!" (And believe you me, I often deliver the line with a Russian-esque, Gru-like accent!) I don't know if it's making a difference yet, but I really want them to learn that tacking the word please onto an order doesn't make it okay.
I also hate it when anyone says, "No offense, but..." because, really, when do you say that that you're not getting ready to say something offensive?