1. Know what 'being polite' means.
Being polite means showing respect and kindness, while being aware of the situation / context. Being polite is a combination of mental & physical habits.
2. Being polite takes practice.
Basically, speak gently, keep an open mind to what others say, and don't be a doormat.
Start with saying "I'm sorry", "thank you", and "Its okay" often, depending on the situation.
3. When someone tells you their name, that's their name. Not their nickname, or their real name, just their name.
Do not rename them.
4. Don't touch people, except in commonly specified way - e.g. shaking hands.
5. Try to smell and look basically OK.
It's more about not being distracting.
6. Learn to use empathy.
Empathy is a practice of seeing other people as they are right now. Be in their shoes before you say or do something. Remember this before speaking to people in any social occasion - a party for example. Listen more, acknowledge their story.
7. Take some social cues from the environment you're in.
For example, people giving their seat to a pregnant women on the train.
8. It is okay to be honest (say what you must) instead of deceitful (fake smiles and all that).
9. Don't try to get an upper hand in any relationship.
It dehumanizes the other person, and becomes a grab for resources.
10. When you are being polite, you are carrying yourself with dignity through life, and acknowledging the dignity of others.
Politeness is not surrender. It is you acknowledging humanity.