Pets... make sure to clean the litter box, remember to remove all pet food when home is being shown. If home has a pet ensure carpets are cleaned really really good to eliminate pet odors
Personal Stuff... buyers don't really want to see your vacation pictures.. how many grandchildren you have or your collection of ceramic unicorns this will distract their interest in your home so remove all personal items and collectibles.
Fixtures. Great time to update any and all worn or outdated fixtures, including lights.. if unable to purchase new, consider spray painting to incorporate a fresh clean look
Window Coverings... Make sure all window coverings are in good repair and not dated or inappropriate for the window type. If this is the case perhaps consider adding simple shear panels to windows... inexpensive and can certainly change the look of a room.