I sympathize with you. It's got to be confusing for boys and men. They used to have films in schools in the 1950s, I think, letting teens know how to express interest in socially acceptable ways. I think the real issue is that people nowadays don't seem to have good manners.

For example, if a man holds a door open, just say thank you. Don't assume he is trying to demean you and give him an angry lecture. He's probably been taught that holding the door is good manners. You can show good manners, too, by holding the door open for someone, particularly if they are carrying heavy packages.

Anyway, simplest way to express interest is just to smile. One would think that is not objectionable, but apparently some women feel that if you look at them and smile, that is somehow threatening. It's not. If you don't like the guy, don't smile back and break eye contact. If you like him, smile back, twirl your hair a bit, look away, then look back. This is flirting. If you are naturally assertive, feel free to go over and start a conversation. It's the 21st century, you don't have to wait for him to approach.

What is NOT OK - men to aggressively pursue you if you tell them you're not interested. Men who try to touch you when you've made it clear you do not want to be touched. it is perfectly acceptable to be rude to these jerks because they are being rude to you first. Also, you are not obligated to sleep with a man simply because he buys you a drink or dinner.

At the same time, you should not take advantage of men and lead them on just to get free drinks or dinner. If you don't like a guy romantically, be honest with him. If you don't like him even as a friend, don't hang out with him at all; if you'd like to just be friends, let him know and offer to set him up with any friends who might like him and ask him to do the same.