I've used the "CAT" scales many times. I agree with the method for two ways previously stated but I would make one change based upon my personal experience. I was charged $10 for the first pass weight and then an additional $2.00 for the subsequent weighs. Each time I went they wanted me to come inside after the first weigh and get my "Ticket Number". The for the subsequent re-weighs I was instructed to yell up to the speaker "Re-Weigh for Ticket No.xxxx"
Lastly, for any Travel Trailer owners looking at this message, you need to do 3 weighs (2 for a fifth wheel). For a TT, first pull thru with TT connected and your WDH engaged just like you would be traveling. Then pull around back and disengage the WDH. For the 2nd weigh you will be no-WDH. This second weigh is what will tell you if your WDH is setup right i.e. enough weight moved to the front axle and rear trailer.
The 3rd weigh is the one you do for Truck only. Drop the trailer but keep the wife, kids and stuff in the cab. This 3rd weigh is what's going to let you calculate your tongue weight and % tongue vs. total Trailer weight.