Amsterdam Central Station has lockers for your luggage, in the East part of the station.
The lockers are self-service, and you can pay only with debit or credit cards (no cash).
Assistance is available from 7am to 11pm, 7 days a week. Outside these hours, usage of the lockers is at your own risk (there is no help available then).
See the picture of the text in the locker station, for prices and dimensions of the lockers.
Luggage lockers at Central Station
Text lockers Centraal Station (date: July 15 2015)