To clean a piano properly is not only from the outside appearance , internal area can hide many dust and foreign objects , some time mouse can brought in things to surprise you.
To do it , one must know how to open up all the front panel and bottom panel, remove all the keys carefully .
Use a vacuum cleaner to suck out major dust , with a brush to clean necessary area. Be careful not to direct vacuum the rounded red and green color felt and cloth, as well as the papers underneath them. Once mess up, you need to spend money and time to look for an experience piano technician to regulate and reset the high and dept of the keyboard and so on.
Never use damped or wet cloth to wipe inside the piano . Certain part is sensitive especially the piano wires will get rust if gets water.
If not sure . Call a local piano technician to do it for you.