I work at a company which does lots of laboratory work, so you can imagine the working place to be quite strict. However it's not THAT strict where everybody wears a suit and I discovered two colleagues at different departments within the building are actually in a relationship which everybody is aware of. This gives me a bit of hope I can flirt with this cute girl I met, but I have no experience with flirting at work. She is from a different department and we occassionally see each other. I introduced myself to her group and sometimes I lunch with them. How can I build enough comfort to ask for her number and eventually a date?

Thanks!