I had my neighbouring vendors spill coffee and coke (2 separate occasions) on my curtains, only one offered to have them cleaned.
Every show is different, all you can do is be as best prepared as you can, and as Chimelle says, expect to have to be flexible and creative at times when problems occur.
I found that I started having less problems with set up when I
a) Requested a particular spot or area; it didn't always happen but I usually end up with a better spot
b) Set up early - if you come last minute and there is a problem with your space, at that point there are usually no other spots to move to, and no way to have your neighbours change their displays.
c) Talk to my neighbours - If the spaces are not well defined and either of us have special needs like wanting an aisle between us, or a rack near to the the edge (or out in the aisle), we can come to an agreement instead of being irritated about how the other person set up their booth, and is affecting traffic flow to ours.