1. Model the behavior yourself and emphasize the please and thank you. This is especially important for younger children as they really do mimic and copy our behavior.

2. Repetition and reminding them- it may seem unnatural and maybe taxing at first but stick with it - the younger you start the better as well. As with most communications, it’s not what you say but how you say it. Make the reminder/ correction as natural as possible. It can be as simple as after they ask for something you say please and then they repeat it and eventually they will adopt it. From my personal experience with my daughter and older stepchildren it may seem that your efforts don’t make a difference but all of sudden it will click.

3. Incentivize the use of the words - the concept of being polite especially to younger children can be hard to understand. Why do they need to use a fork for example when their hands work better or easier?  The same is said for using please and thank you- does it make a difference beyond being polite-  to them, it may not. To support that it is something that they need to say you can make a please and thank chart where if they say please and thank you so many times a week they have a special prize or extra dessert or more iPad time. You can also do a ladder system where with every please and thank you they are getting closer to a larger prize- maybe a dinner out or a day at a park etc...

Once the behavior is adopted you will not need to continue with it- this system is useful for other manners as well- table manners in particular.