The only way to know for sure is to just straight up ask him. Guys to a lot of weird stuff that you might think is flirting, and you wouldn't be wrong to assume is flirting. Like once I was walking down the hall at school, and this dude (I'll admit, I had a bit of a crush on him.) he just started walking next to me, and put his head on my shoulder. Then he like linked arms with me and I was like "Woah! This dude who I have a crush on likes me?!" then I remembered that he had a girlfriend, and then I was really confused. My point is, guys can be so stupid, and confusing, but girl, just ask him. Don't assume. That'll just make everything worse, trust me.
He'll either stare at you for a while or try and not look at you at all. If you two are talking or even nearby each other, (if he's at least somewhat shy) he might have his hands in his pockets and get quiet- he'll just be kind of awkward. If you two start talking, in some cases, he will do anything to evade eye contact. If you guys talk a lot... Well, I've never gotten that far...
They would look at you for excessive amounts of time and when you look at them they would maybe look at you a little then look away. And he might look back up for a second then continue with his stuff and whatnot. It's all in the eyes.
A beautiful girl does something to our senses .. We think awww she will never go for somebody like me pretty girls such as yourself have so much power over us ... And you dont know it so to answer your question is we are all different we use different approaches it can be a note a small gift a smile