So i like this guy at work but how do i move things forward?

Im 17 and i like this guy at work and have been working there for around about 2 months now, we both tease each other a lot but thats about as far as it goes. The problem is im unsure if i should ask him for his number or wait until he asks for mine or do what exactly? I feel like a little kid really but im really indecisive and cant seem to make up my mind on what to do