On your list of things to see in Prague, should definitely be the Old Town Square.
Said to be one of the finest in Europe, the square is ringed with historic buildings and as it is pedestrianised, you only need to worry about the odd horse and carriage.
The impressive Gothic steeples of the Church of Our Lady before Tyn make for some beautiful photographs.
Other highlights are the Astronomical Clock and Calendar on the Old Town Hall Tower. The chimes on the hour are worth a watch, but try and get there for the six or twelve for the most impressive display.
I would suggest taking a couple of hours to mooch around and soak up the atmosphere, grab a bite to eat from one of the food huts and make use of your camera, which is exactly what I did!