If you buy appliances at an outlet or scratch-and-dent sale, pick them up (or have them delivered) right away. Leaving them in the outlet gives them more time to get dented/scratched even more. Also, if you leave it there for a while, make sure they filled out some paperwork, demonstrating what scratches and dents were present at the time of purchase.
When buying an old house, get the chimney swept. Then grab a flashlight, and take a look for yourself. If your house is like ours, the chimney was given a sprayed-on concrete liner, which looks a lot like kreosote!
Check all the switches before you move in. If you can't figure out what that switch is turning on and off, try to find out from the sellers.
When blowing insulation in your attic, wear safety glasses to keep the particles out of your eyes.
When having your walls insulated with product that is wet during installation, consider how the moisture will escape and if it will effect your wallpaper or siding. Also, consider if the moisture will be trapped behind wallpaper or paint. This might be a good question for the contractor or supplier.
When removing a garbage disposer, be prepared for a smelly mess.
Include dining out on your kitchen remodel budget.