Everyone has offered such great advice so far, and I know you can do this!
Never cut out things you love -but shouldn't eat- cold turkey. If you totally deny yourself, say, chocolate you'll eventually end up cracking and binging on chocolate. It's okay to reward yourself with your favorite food or snack every once in a while. It won't kill you. And yes there is a huge calorie difference in regular and diet soda. I managed to lose a little weight by making small changes like drinking diet soda and taking the stairs or parking farther away from Wal-Mart than I normally would

Of course, now I have Crohn's Disease and my whole diet got flipped upside-down. I can't diet like normal people
Drink lots of water!!! It will help with the water weight and whatnot. Avoid low-carb!!! It's horrible for your liver, among other things.
Good luck and know that you have a host of sisters behind you!
ZL,
Meghan