Just wanted to add a few suggestions:

1) Divide the Halls by days. For example I always visit the North hall on Monday, Central on Tuesday and South on Wednesday. Thursday is a floater. This cuts down on needless legwork! Book any appointments with vendors on days corresponding to the hall they are in. You do not want to be in the north hall and realize that you need to meet a vendor in 5 minutes in the south hall!
2) Booking appointments with vendors: the good and the bad. I’ve found that booking time with our sales rep at a booth helps us get the info we need, get in on demos for us (and not looking over someone else’s shoulder) and get time with the product specialists. However, booking too many meetings can also be a pain. You’re always having to leave an interesting demo because you have another appointment to get to.
3) Shoes. You’re absolutely right about wearing comfortable shoes. I swing by my hotel room before going to dinner to dump all the brochures and my iPad. This is also a chance to change socks and shoes. Putting on a different pair seems to help your feet by shifting the pressure points around.
4) Hydration: There are many booths that provide free bottled water. Grab them !