How can you tell if he is into you? If so should I make the move, or wait?

Okay, so I just started working at fleet farm, literally!! I've been working there for like 4 days. While I was training, I needed a cashier to stand with me in case of questions, this guy Kris was igned to stand with me. We talked and I thought he was like in his 20's turns out he is 17...I'm going to be 17 in 2 months. He never stopped smiling or laughing while we were training. Today I was on my own, and he was in the check- out lane before me. We talked and everything , it was great. Then I would notice him looking at me while I was working with customers, or just standing there, then I would look and he would turn away. He finished his shift and bought m&m's and something else and waited in my long line in the middle of all the checkouts (8) instead of going to the small line by the door!! I told him he just came to my line to see me and he smiled and was like sure, then started laughing. He joked with me for a bit then had to go. Is this the start of something? What do I do???