The good news is that you drop about 15 pounds on the day the baby is born. The weight of the baby plus the weight of the fluids lost during birth will total about 15 pounds, so that is a quick fix weight loss to look forward to. So, you start to drop weight the minute the baby comes out.
After that, it depends on each woman. You will be so busy taking care of the baby, that you will get plenty of "exercise" just moving around taking care of the baby.
Since you have already successfully lost weight in the past, you already know how to eat to drop weight. BUT - remember if you are going to breast feed, you will want to be sure you are getting plenty of nutrition for that.
Personally, I never tracked my weight loss after the birth of the baby. I was already fitting back into my pre-pregnancy clothing within two weeks after delivery, so I never paid any attention to the weight on the scales.