The standards of polite vary, depending on many things. Who are you with? Where are you? What are the expectations in that time and place?
Most importantly remember that no matter what the standards seem to be, no matter how they seem to be changing, some things are always rude. Some ways of acting are always polite. Holding the door for the person behind you is always polite. Looking someone in the eye while they are talking to you is always polite. Texting at the table is always rude. Texting while someone is talking to you is always rude; despite the fact that people seem to think its fine. When you are talking to someone, look them in the eye, give them your full attention. Dropping a call to take another is always rude; the second person can wait. Return your calls and answer your e-mails. And though they may be old fashioned, thank you notes make people feel really good.
A little trickier is the whole man/woman dating thing. Different kinds of women, raised in different kinds of home, expect different kinds of politeness. But trust me, offering to pay for a meal on a date is always okay. Opening a car door is so old fashioned that most women will love it. Walk on the street side so you get splashed, run over, whatever, and not your date. Pull out her chair in a nice restaurant and let her precede you through a door. Most young women will never have been treated with that much respect. But remember it is rude to treat women as different or less than equal. If she wants to pay, let her.
Remember the Queen of England expects a curtsy from the girls and a bow from the boys. Everyone rises when the President of the united States comes into a room, and they remain standing until he sits; its a matter of respect. Old folks go ahead of you and you always offer to help the helpless when you see them. Simple rules for the big things. Not so simple for all the things in between. Be respectful and pay attention to where you are and what is expected of you and by whom. Life’s an interesting dance, always make your partners feel special. Please and thank you are still the magic words.