Make eye contact, laugh or giggle at him, compliment him, and probably the most important thing, spend consistent time with him. If you do all these things and then don’t hang out with him or don’t go out of your way to try to insert time with you into his schedule, men will consider it a one-off thing or won’t think of it as flirting. If you show interest in his hobbies and ATTEMPT to spend time with him, saying you wanna spend time with him, and do all stereotypical women flirt stuff, you win