A spotless home makes a strong impression on a buyer. While some level of dirt and clutter is endemic to life in the home, the fact is that the less "lived in" your home looks, the better it will show to buyers.
Consider a furnished model in a new home development - the furnishings and appointments give the look of a finished home - without the wear and tear of actual occupancy. Try to come as close to that level as possible - you'll notice the difference in your sales effort.
Hire a Professional
Making sure your home is clean is a crucial step in the marketing process. It's also a very time-consuming process - one that many people don't have the time or motivation to tackle properly. Hiring a cleaning service is almost certainly worth the cost if you don't have the time to do the work yourself. It may even make sense to arrange for regular cleanings during the selling period.