The best way to travel around amsterdam is definatly by bike. There are a few companies that rent out bikes and they are not hard to find, you'll see adds all around the city. However be careful because so many bikes get stollen everyday. Make sure you lock your bike with a chain to something solid and that the chain goes through your front wheel and the main frame of your bike. If your staying in amsterdam fro a while it might even be worth buying a bike...the best place to get a really cheap 'second hand' bike is either from the station or from the biggest flea market near waterloo plein.
Enjoy!!!!