[header] How to flirt with a girl you work with [title] Smile at her. [step] It's simple, but smiling and being polite and kind are great ways to subtly hint that you like her. Workplaces are professional atmospheres, so livening up a bit and being friendly and outgoing could set you apart to her from the other people at work. 
[substeps] A simple smile or joke is an appropriate form of flirting, and doesn't cross any professional lines. If she smiles back and goes along with it, you know she's into it.