Pre-op prep: I had a BMI >40, so I was on a one-week, protein only, low-carb, low-fat diet to shrink my liver. I did mostly protein drinks, broiled chicken (just bought a roasted bird at the market and picked at it), salmon, sole, cottage cheese and non-fat plain yogurt- mainly just to keep it simple. Fish and other meat is ok too, as long as it is low fat. Boring but very doable after the first day or two - because I wasn't really hungry. I lost about 7 pounds during the week of the pre-op diet.
I also spent some time pre-op pulling together my vitamins and post surgery supplies. I made and froze a batch each of very rich and concentrated low-sodium and de-fatted beef and chicken stocks and bought some sugar free jello, pudding etc. I already had protein drinks which I have been using for a while, so didn't really need to stock up. I collated a bunch of WLS-friendly recipes for when I am able to eat again and made lists of options for full liquid and mushy stages of the post-op diet.
I was actually not feeling nervous or anxious about the surgery, but did make sure my will / living will were updated and accessible just in case. Also made sure my family had the contact info for the hospital and hotel. Your room at the hospital will have a phone, so family and friends can call you there through the hospital's direct line.
I live in Canada but visit the US frequently and have a pay-as-you go US cell phone (Virgin Mobile) so I charged that up and brought it with me. It worked fine from the hospital (with an American provider, so no roaming charges) but not from the hotel.
Finally, I took my weight / measurements and a set of front back and profile pre-op photos so that I can track changes over time.