You all must have heard ""Monkey see, monkey do"", that's it! Young children learn best by imitation. It is vital to be the role model for the behaviour that you want to see in your child.
Me and my husband try to use these words while conversing with each other and with kids. So for them, it's a part of our normal conversation.
Our children learn by our actions, not by our words. But of course, do not expect complete obedience and etiquette from them all the time. There are days when Arzu & Kabir fight with each other and just refuse to apologise and that's ok.
Never force your kid to show any specific kind of behaviour and never compare them with other kids. Sooner or later they'll learn everything.