Honestly the best way to keep a woman is to be a man. //content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif
It doesn't always work, but it is a start.
Don't be one of those guys that doesn't care at all. (The guy who treats his girl bad, don't do that) But, you have to lay down the law & wear the pants. She doesn't want you to cry even if she says so. She doesn't want you to go shopping with her even is she says so. She doesn't want you to hang out with her friends, even if she says so. Pretty much what society tells women what they want in their man is totally different than what they really want. Basically, do what you would do if you were single and she was a good friend. But, make sure she knows you love her (if you do). Oh and give her space if she needs it, if she needs space and you keep hounding her you are killing it on your own accord.
And if it doesn't work out. Oh well... There are others out there. Fighting for love if she isn't in love isn't ever going to work.