Nope, it varies for every women so there is no "one size fits all" when it comes to winning a woman's heart. Say something that is personal to her, something that shows you know her and that you've been listening.
Tell you what-take the time to really listen to what she is saying. You would be surprised at how few guys actually do that. She will remember you for that alone. Whenever you are around her touch her arm or shoulder. nothing to suggest sex, just letting her know you want to touch her and be near her. Ask her how her day was and listen to her answer. Don't try to fix her problems. She needs someone to listen to her problems and how she feels about whatever they are. She doesn't need someone to fix them. If she did, she would ask. She needs a sounding board, and someone to realize she needs to vent once in awhile. Surprise her with a silly gift, Call her during the day just to hear her voice. Anything that lets her know you were thinking about her. And say, I love you more often.