On arrival at Hoorn, I went to the Information centre and bought a walking map of Hoorn (cost 2euro) This showed me the way past the major sites and gave information on them. I saw a few city gates, and lots of buildings with "decorations" on them.
A cheap way to get to Hoorn is by the Bus. The Bus leaves from the Bus Station near Central Station. If you are standing facing the Station, then its the bus station to the right. Here you will find the Buses and signs of where they are going.
For good value BUY THE WATERLAND TICKET. It lasts you a whole day covering the Waterland area. You can get on and off the bus as much as you want, as long as you keep using the "Arriva" Bus company.
You buy the ticket from the Driver as you get on the Bus, and just show to each driver at your new destinations when boarding the Bus.
Cost in 2009 was 7euro FOR A TICKET FOR THE WHOLE DAY.
There are family passes available as well