I'm no real estate agent, but I do know this: if you want to sell your home, it can't be cluttered. Any potential buyer will be turned off by a crowded, dark or overly personalized house.
Declutter the closet. Remove about 50% of your belongings from the closet to make it appear larger. Store your items in well-labeled bins so that you can find the things you need and/or donate what you don't need anymore.
The kitchen is key. Remove everything from the counter tops except for the appliances and maybe a fruit bowl. Removing everything makes the countertops appear bigger.
De-personalize the house. Remove and store any personal items. This allows the buyer to imagine themselves in the house..and not you. Go ahead and pack these away to be moved (since you're at it anyways.)
Curb Appeal is important. Clear any kids toys, sports equipment, etc. And don't forget the side yard. Clean up any misc gardening clutter, haul old building supplies away, and finally - make that trip to the dump you've been meaning to do. Have a backyard storage unit? Clear it out. Curious buyers WILL take a look.
Hide your pets. We think they are adorable, right? But potential buyers do not. They may be scared off by potential pet smells, or allergies, too. Put pet bowls, litter boxes, pet toys away (even offsite or in your car), and make sure to clean pet hair off of furniture.
Use lighting generously. Everyone wants a bright, cheerful, house. I you don't have a lot of natural lighting, be sure to bring in lamps so it seems brighter all around, especially in darker corners.
Tidy up the garage. Get your stuff off the floor. Place your storage items on shelving and/or utilize labeled storage containers. Make your storage areas look as organized as possible - something for the next buyer to aspire to.
Fix the easy stuff. No need to embark on a major remodel, but if there are little items you've been meaning to get to - now is the time. Even chores like washing windows, changing the electrical switch plates and adding a fresh coat of paint can really freshen up a home's appearance, without costing a lot of money.