Interesting that nobody really did tell him what to expect and answer as he put it "How screwed" he could be... Well, It's been a while since I've been on the board - so I'll take a shot at this one.
What to expect: You follow the signs and lights and it's not a bad idea to roll your drivers window down a little bit in case they have a speaker outside to alert you of something... Like "Park and come inside" or the rare "Have a nice day".
Now, for future reference there's something called "Trip planning" that is a helpful thing to do. Check your route ahead of time and find the scales, in those areas you should have your log book AND Inspection book/sheets current- Very Current, especially the last 7 (Seven) days.
Make sure before you leave on your trip that your brakes are good, the alerts/buzzers come on at the right air pressures. If the truck does not have air brakes then make sure the brakes are adjusted properly... and with him working around equipment a good bit either he knows or he knows somebody that can help him with this.
Tire tread depth, make sure you got it and you are above the wear bars.
Make sure ALL of your lights are working, and working the way they are supposed to work.
Belts and fluids should be good, and it's not a bad idea to make sure there's no leaks.
If your rig has air power, and there's air going to a trailer, make sure there's no air leaks... if there is, then find it and fix it. Why? Because, if you don't find the air leak and the DOT/Scale Master finds it - you can put money on it that your trip just got worse.
Be polite, don't speak too much. Use good manners and it's never a good idea to curse in front of a DOT/Scale Master. Basically, they're like a police officer or Sheriff Deputy except much more powerful when it comes to a CDL holder... which can be expensive and/or aggravating.
For a long trip, it's also a good idea to keep a clean cab - it throws up a red flag and makes the officers at a scale more suspicious if you open a door (Any Door) and trash or a mess falls out and/or is in clear view.
Prior to getting out and walking inside to a scale house it's also a good idea to freshen up some - and look at least half way decent... in other words don't look like you just cut grass with a push mower for 3 hours. Do Not Smoke or chew dip going into or exiting a scale office.
This should be a good start for you and hopefully others will chime in with other helpful tips/advice.
BigBusBob
