Last week a parent asked me how to handle teaching her 3 year old daughter to say "please" and "thank you." We all want our children to be kind and respectful, even when we aren't always so ourselves. "Angie" is a typical 3 going on 4, full of energy, alternating between garrulous and shy, ready to embrace the world when she's not hiding from it safe in mom's arms. Her parents are good natured and down to earth world travelers, who speak three languages that I know of. Angie is able to understand 3 and speaks mostly in her mother's native language, but communicates well in English.
Her parents and I had discussed various parenting styles and at one point I used their own specific example to help them understand my problem with the use of rewards and punishments to train children. An aunt had come to visit and brought toys the first time. The parents were concerned that Angie would be disappointed if auntie didn't bring a gift each time. I pointed out that rewards tend to cause this kind of problem in discipline. The child's behavior is externally focused, not internally-- she treats auntie well because of the gift, rather than because she is just happy to see her. In the same light, when a child isn't ready to say thank you, pushing them only increases the social tension. But you don't want a rude child! "What do you do then?" they asked, and I said, "you let the child off the hook in the moment, and prompt them to see it from the other person's point of view." It wasn't long before we had a chance to try this skill.
Angie was very excited to meet me, but when it came time to show gratitude to me for sharing something, she clammed up. I could see she felt a great deal of stress, and couldn't bring herself to speak despite daddy's prompts. So I told her, "That's ok, you can thank me when you're ready." She smiled and, looking a bit past me, said thank you in a quiet voice. It took her a while to warm up again after this bit of social anxiety.
Had she balked further, the best thing to do would be a simple conversation from mama or daddy: Do you like it when people thank you for sharing? Yes? How does it feel when they don't thank you? Is that how you want your friend to feel? No? Then what do you do? Most children Angie's age are able to follow this emotionally and come up with a nice "thank you."
For younger children, please and thank you and other social niceties are mostly imitative. That is, if you and the adults and other children around them are saying it they will happily say it all too, as soon as they are able to. Even contrarian 18 month olds can be encouraged to be helpful and use these basic elements of manners, although consistency doesn't exist at that age. Repetition here is your friend, but remember to be low key and low stress with this kind of prompt.
As for rewards and punishments: you don't have to, for example, give your child a toy if he's not behaving well, in fact I don't recommend it. This is not the same as punishing him; it's a natural consequence of his behavior. Don't couch it as withholding the toy because he's bad. It's better to say, "I'm not sure you're calm enough to have the toy yet. Can you show me how you calm down?"
On the other hand, taking away a toy to punish him can backfire. "Ha, I don't need that toy anyway!" is a response they come up with pretty quickly. Next thing you know, an inexperienced parent will find himself in a power struggle. And that, dear readers, is something you'll want to avoid. Once you let yourself get drawn into a battle of wills, you've already lost.