Like others posted, look up, down, over, under, inside, and out, at everything. Make sure you are shown and check the operation of every system, every appliance in the rig. Ideally, the dealer will have the unit prepared for your inspection as if you were at a full hookup campsite and the refrigerator will be in operation, with thermometers in both freezer and fridge sections (our trailer was even hooked up to sewer for the PDI). And most of all, take your time, even if the dealer tries to rush you. When we bought our new TT, I told the tech while I was familiar with RV's (we had a fifth wheel), I wasn't familiar with THIS RV! Our total time at the dealer for PDI: Just under 4 hours, plus another hour and a half for hitch install and adjustment. The dealer's staff did a great job and we left satisfied customers.
And, if the weather permits in your area, take it out to a nearby campground if open, for weekend shakedown cruise, in case anything did escape your attention at the PDI. Most important, enjoy! :)
