With Amsterdam as busy as it is it's a good idea to plan ahead when looking for a place to stay. Ibis Hotels, who offer basic but comfortable rooms, have a new deal called "Happy 30". Rooms in Amsterdam are offered for 49 en 69 Euro when you book at least 30 days in advance.
Ibis also introduced this campaign in 15 other European countries. The interactive maps will tell you where the hotels are located exactly.

So plan ahead and save some $$$!