Hello, Andrea!
I copied this response that I gave to a similar question back in July. Hope it helps you . . .
The nurse at my pediatrician's office gave me some advice that worked out really well for us. She prefaced this by saying that if you ask ten different nurses, you will get ten different answers, but like I said we took this advice and it was helpful to us . . .
She said at this point, you don't want to do anything to make the bottle more appealing, so don't put milk in the bottle. Only give milk in a sippy cup. Make a big deal of it and offer it after a meal like a dessert (because milk can be an appetite suppressant). At the same time, start diluting the regular formula bottles, so your son will become less and less interested in them. We did this over a period of about a month- six weeks (3/4 strength bottle, 1/2 strength, etc.)
Another important thing to remember is that your son won't be drinking nearly as much milk as he did formula. He will be starting to get more and more of his nutrients from his solids, so don't be worried if he isn't taking the same number of ounces of milk that he did formula. Also, some kids just don't like milk and never become big milk drinkers. That's okay, too, if they can get their dairy from yogurt, cheese, etc.
Our son started out slowly with milk, but now he guzzles it. Using this method, he was off of a bottle completely within six weeks (at 13 1/2 months). I hope that helps. Good luck with the transition!