During the previous nine months your body was more than likely depleted of needed vitamins and nutrients that it needed to stay healthy. In order to get healthy, and lose weight, the first step is to get yourself eating healthy. For most women, this translates as eating nothing, but that isn't what that means. Eat proper, nutritional food that adds to your body instead of sugary, high-carb food that doesn't add any needed items to your body. When you have the urge to splurge, do so, but do it as healthily as possible.
Exercise is the key to sucess.
With a newborn it is hard to find the energy to exercise, let alone get all the rest you need, so you find that you don't exercise at all. I warn against this. It will only make your recovery harder. My husband and I got into the habit of walking in the late evening. Of course, walking isn't that only exercise that your body needs to tone up those loose muscles and flabby legs.