If your carpets are worn out or have rips it can be a big turn off. Consider replacing your carpets, choose a light neutral color. Another alternative is if you have hardwood floors under your old carpeting if to have them refinished. Take a critical look at your kitchen. Formica counters which are out-dated can be replaced and at the same time change the whole look of the kitchen.
Older cabinets can receive a face lift by just replacing the knobs.
Decks and patios cleaned and repaired. Boxes neatly stacked in corners. In this case less is best. Very simply put, if your not using it pack it away. One of the first things a buyer will look for is ample spacious closets.