Negotiate every aspect of your contract, some contractors will hold your feet to the fire on the contract (i.e. unless you state you will not work 7 days a week, 18 hour shifts, you will work every day you are there).
Also find out what your method of transportation to victory and from will be. You do not want ground, and most contracts don't do anything other than air anyway.
Will your contract/job require you to "go outside the wire"? Unless you work for a private security company you are usually very restricted on leaving the base (that is a good thing).
The mail is your friend. You can get anything in the mail...enough said.
You will not be allowed to carry a weapon unless you work for a security contractor. You don't need one. People aren't jumping over the walls of the compounds.....they are dropping mortars and rockets over them. You will be issued body armor and a ballistic helmet. Learn to wear them properly. The soldiers will laugh at you if you loook like Gomer Pyle.
It's a good opportunity if the pay is right. Also get in while the getting is good. My .02 cents is that this gravy train is about to come to and end in the next couple of years.
Hope this helps.