Little things mean a lot, especially to a real estate agent who is trying to sell one listing among many.

Two things that may seem little but are really not so trifling when it comes to selling a house: keeping it neat for appointments, and washing the windows.

"The marketplace is monopolized by first-time buyers as well as empty-nesters," said Mark Wade, who sells houses in Center City for Berkshire Hathaway Home Services Fox & Roach Realtors.

"Both sets of buyers have one thing in common," Wade said. "They look for turnkey properties; therefore, condition is king, and a strong showing ability is the key to value in Center City."

That's true everywhere else, as well, and it has a lot to do with the way prospective buyers tour a house for sale.

"People tend to spend no more than 10 to 20 minutes going through a house," said Leonore Spinelli, an agent with Century 21 Alliance in Moorestown who is a residential interior designer and "virtual stager."

"They are looking at the space and flow of the home," Spinelli said. "If the house is well-kept overall, they may not notice that windows that have not been cleaned recently."

But, she added, "cobwebs, bugs in windows, and dirty screens may be indications that the home has not been cared for in other areas. These are peeves of mine when showing a home."

Marilou Buffum, associate broker with BHHS Fox & Roach Realtors in Chestnut Hill, said she doesn't notice windows "unless they are awful."

However, "the difference between clean and not clean is dramatic," she said.

Clean windows are most important in the fall, when the colors of the leaves shine through and "you can see that they are dirty," Buffum said.

Dominik Palaszewski is "chief cleaning officer" of Sofian Cleaning Services L.L.C. in Philadelphia, which he and his wife started 11 years ago as a housecleaning service, "but we were finding great demand for window-washing, so we added it on to the business."

Sofian has a special program for real estate agents for cleaning and maintaining listings while they are on the market, Palaszewski said.

Windows should be washed at least twice a year, he said.

In the high-rise condominiums of Center City, that is the usual routine, area agents said. Yet twice a year is rare for most houses.

Windows in the city tend to get very dirty from dust, grit, and vehicle exhaust, while at properties with many trees pollen gets stuck to windows and makes them tough to clean, Palaszewski said.

Joanne Davidow, vice president of BHHS Fox & Roach and manager of the Rittenhouse Hotel office, said keeping old windows clean can be a chore.

If you can't replace your windows, make sure they operate properly, Davidow said, because buyers demand that even older double-hung models work.

If a client has old windows, Lisa Fazio of Weichert Realtors in Jenkintown said, "I open and close every [one] so a home inspector won't pick it up, even though a window painted shut is considered a cosmetic item."

To wash windows, Palaszewski said, he and his crew often must use a knife to break through layers of paint that have been applied over the years.

Not only does he wash the windows inside and out, but he cleans the frames and the bottom ledge, which tends to get the dirtiest, routinely.

Storm windows are washed, as well, he said, and the screens are cleaned, too.

A rambling house with 30 double-hung windows and storms will take a full day to clean, while the same number of new windows will take half a day, he said.

Sofian charges $8 for a new window, $12 to $15 for a double-hung, Palaszewski said, adding that his prices "are pretty standard."