Don't let these things devalue your home. Be prepared when it's time to sell!
The first thing a potential buyer of your home will see is the outside. First impressions are sometimes all that matter to people; and a better outside will at least get more people to take a look around inside. Have great curb appeal, and a neat, nice-looking exterior of your home.
Some of the most important rooms in your house are the kitchen and bath. If you can't afford a full remodel, update them and freshen them up as much as you can with new paint, fixtures, lighting, etc.
If you are thinking about selling your home, get rid of theme-driven rooms. These will assuredly drive away potential buyers.
Pets & Odors
If you have pets in your home, make sure you're thoroughly cleaning your home so it doesn't look (hair, etc) or smell like pets live there. Also, another big turn-off is if you smoke inside your home. Get rid of all unpleasant odors. If someone can't breathe in your house, they won't bother looking through it.