If your walls are not in pristine condition or the paint color is unique paint them a neutral color. A fresh coat of paint will make the place look better an a neutral color will appeal to the most people. If the carpets have stains or are worn, consider having them replaced or at the very least have them professionally cleaned.
An old real estate trick is to replace lower wattage light bulbs with higher wattage bulbs in hallways, bathrooms and other locations that would be otherwise dimly lit. A brightly lit room looks larger and more inviting. Its an inexpensive trick that is well worth it. Leave the porch light on at night. You want people to notice that your home is for sale.
You never know when a potential homebuyer will drive by.