If you’re looking for subtle hints (these are old school but, I’m old and I think they still work.)
Smile when you see him and make eye contact
Listen to him and respond to what he says. Let him know that you really care about what he has to say.
Ask questions that allow him to talk about himself. Ask follow up questions when he reveals things about himself.
Touch his hand or his shoulder when opportunity arises.
Touch your hair.
These things seem silly and simple, but they are “flirting signals,” and are non verbal ways that we communicate interest. Some people do it naturally and sub consciously.
Many moons ago, when I was in Jr High, My first love told me that he knew I liked him when we were in the library an he bent down to find a book and I bent down to help him. Sounds weird, but that little thing I did naturally communicated something to him.
I wish I could find a better word than “flirt,” that’s the only word I can think of for the natural “courtship dance,” we humans do. It comes really easy for some, and others have a tougher time. I did these things sub consciously when I was interested in a guy. Now that I’m an old married woman and have had many years to observe, I have noticed the specific behaviors that made me a “successful flirt,” back in the day.