Simple good manners govern the way we interact with others, and can begin in the home. There are a number of books which you can read with your daughter to help her understand why manners are important. The Elephant and the Bad Baby is a terrific story about an elephant and a baby who go on a food-stealing spree.
The fun of the book is that the elephant is happy to steal buns and ice cream at the baby's behest but refuses to continue when he realises that the baby hasn't said "please". For slightly older children, Madeline Says Merci by John Bemelmans Marciano contains advice written in rhyme form. The Madeline cartoons will be familiar to children and the illustrations lighten the text.
Once your daughter understands the importance of basic good manners, you can remind her gently to say "please" when she asks for something and "thank you" when she receives something. After a while, stop reminding her so she stops relying on your prompt.
If she forgets, you can step in; but the aim is for her behaviour to become second nature. As a foundation, start your daughter off by focusing on greeting people, asking courteously and thanking them.
Good manners should be applied in all your daughter's dealings. It saddens me when I see students being discourteous to domestic helpers and staff in restaurants.