How to go past a "Hi, how are you doing?" with a coworker?

This is my first time posting here. I've been working in this new retail job for almost 4 months now and there's a guy that I really like and he's new too. At first he didn't say a thing even though I smiled at him and said "hi" (I think he's shy and I'm kinda shy too) but since 2 weeks ago he greeted me with a handshake and asked how I was doing and then left.And now he always smile and greets me every time he sees me, I don't want to sound like he likes me because I know this is very common for guys to do and I do it too with my other coworkers. The thing is that there's something special about this guy and I really want to meet him. I can't help but feel stupid because everytime I see him I get nervous and I just can't seem to go past a "hi, I'm good".Last week I decided to take my first step and went to his area to get "something" (of course it was an excuse) and decided to ask him something trivial about his job, he nicely replied and he asked me the same question. We chatted for less than 2 minutes but I felt so good. Two days later I wanted to talk to him so badly but I didn't have any reason to go to his area, so I decided at the end of my shift to buy some candies and chat with him a little (sometimes he's at the checkout). He remembered the things we chatted about last time, which was really cool, and I can't help but feel he was a little nervous too.So, my question is, how would you guys approach someone to go past a "hi, how are you doing?". I really want to meet this guy but our work conditions make it impossible to chat while working. Should I try to talk to him as soon as he gets in the store? do you guys think he's just being friendly? I though about asking him for his Facebook or any social media just to try and chat more outside job but I feel like it's too soon to ask for that info and I don't want to be seen as a stalker. Any tips are appreciated.TL;DR I like a guy from job and don't know how to start a conversation.