You want to look over the apartment closely and make a note of anything that is not working properly or is broken. Areas to pay attention to include the following:
Smoke and CO2 detectors are working
Check around showers, tubs, sink, toilets, and in the basement for mold or signs of water leaking in from the foundation
Check walls and ceilings for holes or signs of water damage/stains
Check for broken windows, windows that won't open, and that the window frames are free of cracks and sealed properly
Check every light switch and outlet to make sure they work
Check toilets, faucets, tubs and showers to make sure the hot and cold water work and they they drain properly
Check that all appliances turn on and operate properly
Check to make sure the hot water heater, furnace and air conditioner turn on and operate
Look for signs of pests or mice
Look for holes in the exterior siding and the roof
Make sure all the door close and lock properly
Check that steps and handrails on stairs and decks are secure and in good working condition
Note any stains, holes, or damage in carpet and other types of flooring.