The best presents in general for your significant other are ones she has subtly alluded to wanting in conversation. A prime example from my own experience is last Christmas: every time the girl I was dating at the time would stay the night, she would go on and on about how amazing my goose-down comforter was and how she wanted to take it home. It was a no-brainer that she would lose her shit if I picked one up for her, and of course she did.
Pay close attention to what she says and she'll lead you where you need to go
