If say someone is on the clock, working like a secretary or front-desk job, and you pass by them how can you engage them?

Aside from engaging in basic conversation and attempts at humor, what can you do? I'm sure there's plenty of guys who say "Hi" and make basic conversation. What can you do to stand out? And how can you get it across that you find her attractive/cute without being too weird (as well as introducing yourself).

Is it a bad idea to 'flirt' with people while they are working? Lemme know any advice or tips, I'm lost.