You need to talk to her every chance you get and never take her on a mission (for some reason that makes it impossible for her to love you). Then in the Mages tower make sure you fine "Wynne's lingerie" it will give you +24 with her and initiates the love dialogue.
If you believed that you're crazy, and why would you want to have sex with Wynne anyway? That's just gross.
You can't romance Wynne the same way you can romance Morrigan or Leliana. You can get her approval rating maxed, but you don't get the option to go to bed. --- XBL: TRAIT0R J (it's a zero not an O) PSN: TraitorJ