I like one of the regular customers that come into our shop. My manager has noticed it too (she could feel it a mile away) and i've also talked to my friend who also works there about her.
Now, whenever she comes into the shop, they both have this "look" on their face. Today, my friend even gave me a chance to serve her but i didn't take him up on the offer.
Why not serve her ? Be nice and smile when serving her, she will remember you if you behave 'misteriously' and have a nice posture.
Don't be obvious with your looks and all.
when serving her just make sure youre polite, like ask "how are you today?" "hows your day been?" "have a gd wkend?"(that last one you should only use on a monday, mainly in the morning but can be in afternoon) and ask it with a genuine smile on your face while looking in her eyes. make sure that every time she's in the shop you're stood up straight (good posture does make a difference!) and look like you're having a good time.... you want to be this mysterious guy who must have a great, fun life that he's walking around the store happy as can be. it might be a bit too forced to be all like "hi whats youre name?" sat behind a cash register but i suppose it depends on what kinda shop it is. i think a better way of wording it would be to introduce yourself and then ask hers, e.g. "hi im <yourname>, ive noticed you shop here a fair amount but all this time ive never known your name"... hmmm that might osund a bit dodgy i think youll need some more opinions on that but i would try it like that.