6 month "diet"
I recommend spending the next six months researching the four forms of WLS---the Band, the Sleeve/VSG, the RNY/gastric bypass, and the DS/duodenal switch. Each one works differently, and has a different post-op 'diet'. Since this post-op 'diet' is how you're going to need to eat for the rest of your life, it's VERY important to choose a surgery type that works well with how YOU are happy eating.
I chose the DS, in part because it suits how I like to eat. For breakfast this morning I had 8 slices of bacon and a scrambled egg. For lunch I had home-made pizza---very thin crust, lots of meats and cheeses. For a snack, I had two sticks of string cheese and a handful of walnuts. For dinner I'm having a steak and baked potato slathered with real cow butter. And a yeast roll, also slathered. (*grin*) Before bed, I'll probably have another high-protein snack of some sort.
You should also start taking vitamins NOW, and eating a high-protein, low-carb diet. Unless you're required to lose a certain amount of weight before surgery, don't necessarily focus on eating low-calorie. Focus instead on eating healthy foods.