I run through a PDI, just like I was picking it up new, checking all the systems. I am especially looking for water leaks and appliance operation. I adjust the thermostat as necessary to get the furnace to come on and make sure it will cycle on and off by itself. If I can catch a warm day, I'll do the same with the A/C. I visually check the roof, clean up there as necessary and apply DICOR sealant anywhere it looks like a small seam crack may be developing. I do the same for the seams around the sides, front, and back. I run the slides in and out a few times, run the shades up and down, and check closely for any evidence of bugs and/or mice. I also check tire pressure and spring hanger assembly tightness. Think that just about covers it.
Found one new water leak, two burned out exterior marker lights, and one interior light. Everything else seems fine starting out this year.