As with anything, make a complete and detailed inspection. Check along all interior walls, paying close attention where the walls meet the ceiling, for any signs of water intrusion. This includes inside the cabinets as well.
Look around all windows, doors, etc. for signs of leaks.
Follow your nose! If you smell a musty or mildew odor, then that means there is a leak somewhere.
Make sure all appliances work, that slides work, plumbing, electrical.
Look at the tires, the roof, and all exterior walls.
Yes I know it sounds a bit daunting, but well worth your time and you will be so much happier in the long run. Perhaps someone else can chime in and cover things that I may have left out.
Times fun when you're having flies!
