Slowly. We planned to have her completely weaned by her birthday, so we started at 11 months, but it didn't go well the first time, so we stopped. We started again about a week ago, and it's going better this time. We probably have about a week to go until our last can of formula is gone. She's at about 75/25 milk/formula right now.
Re: transition to milk
I started giving him milk. He loved it. Doesn't even notice a difference. I have formula left but once that is gone he will be on just milk.