The back yard should be tidy. If you have a pool or spa, keep it freshly maintained and constantly cleaned. For those that have dogs, be sure to constantly keep the area clear of "debris." If you have swing sets or anything elaborate for your kids, it probably makes more sense to remove them than to leave them in place. They take up room, and you want your back yard to appear as spacious as possible, especially in newer homes where the yards are not as large.