Can I answer as a straight woman, just to give my pov? Three things come to mind:
1) Be incredibly respectful,
2) This includes not coming on too strong because you could seem creepy or pushy,
3) But make it clear you're romantically interested, not a) simply sexually or b) as a friend only.
Try a mix of traditional-for-a-reason attempts, like a single red rose or a box of chocolates (NOT for a holiday, but just as an "I was thinking of you" message), with some more personal touches that show you know her (or that you want to know her, if you're new in her life) such as a favorite flower or a "How was your day?" phone call.
Compliments are always good and don't cost money. Make them specific so she knows you're not just faking it/trying to manipulate her. Show her you notice things like how hard she works and the shade of her eyes or something nice she did for someone.