3 things to warn:
1. Do not go to the job with all your WD equipment on the truck, unless that is a flood truck only and or you ALWAYS carry that equipment on you. This is only if you're starting out. You may get people saying they have a huge job, but when you get there and take some readings, you quickly find out it wasn't all that big. Once you have your work authorization signed and deductible collected, you can than remove water and or contents, than later come back to remove water and or drop off equipment and so forth. If you watch the bigger companies in your area, you will see they have regular vehicles wrapped, those are the inspectors/estimators, once they get the job, they than call the office and tell them - we need 3 LGR's, 20 axials, yadda yadda.
2. Carry a pair high top rubber boots, pair of clean socks, and a small dry towel on the truck. It's not really a warning, but I hate walking under water in my regular o' shoes, it just sucks. Put the hand towels w/ the socks in 1 gallon zip lock bag so it doesn't get wet/dirty, place the bag inside of the boots, this way if you do get your feet wet, you have an extra dry pair.
3. Always get your work autho, direction of payment signed off before commencing work, and always get the deductible. If you don't get it now, it'll be a nightmare to get it later. Even if they don't know what the deductible is, something is better than nothing. (Most people know their deductible, they may be just testing you and playing dumb). Get min $250 and tell them "later today or tomorrow morning we will be back to pick up the reminder of it before proceeding w/ work or put it on a credit card". You can always call the adjuster on the claim and ask what the insureds deductible is, they have it on their file in their truck/pc, it's not really a "secret" anymore.