Rijksmuseum, naturally. Wander the Jordaan and the Negen Straatjes. Check out the Verzetsmuseum. If the sun is shining check out Vondelpark. Try some local delicacies: Hollandse Nieuwe - raw, salted herring, kroketten, bitterballen, frikadellen, patatje oorlog. Go for an Indonesian feast, a rijstafel. Buy some cheese, but go to Albert Heijn, not a rip off tourist shop.