I know that a lot of people have a hard time telling if the person they're talking to is flirting or just being nice.

I kinda have the opposite problem. I don't know how to know whether the way I'm behaving is being interpreted as flirting or if I'm being thought of as just being nice. Like, i get the idea that what I consider flirting is something that men just consider me being polite or nice.

How do I make sure that the man I'm flirting whit knows I'm flirting with him?

(For the sake of context, I am a straight woman, not a gay man.)