I usually commute to work by the tram, and it involves switching to another tram at Centraal. Ever so often, I either get down several stops earlier after changing or just walk all the way from Centraal to work in Rembrandtplein via the Dam Square and Kalverstraat areas of Amsterdam.
On the lucky days that I am early, I sit down around the area and enjoy some quiet minutes amongst the hustle and bustle.
The Kalverstraat area is devoid of tourists in the morning, which makes for a pleasant stroll. At any other time of the day, it is a full house with barely any space to walk.
Window shopping is a must-do, especially for flowers and clothes.