well I live about 1.5 hours away from Amsterdam
It's a great city! some must see things:
There are loads of museums, from the Anne Frank museum to the sex museum lol, be sure to visit the sex museum it's funny as hell
Don't ever buy weed from someone on the streets! I can't tell people enough cause you'll get ripped off/robbed or whatever. Just go to a coffeeshop. Coffeeshops in Amsterdam sell coffee, sure but they mostly sell hasj and weed.
Make a boat tour on the canals, really nice and affordable way to see alot of the city.
Visit the red light district, but dont go alone when it's dark!
A nice place just to hang out a bit is de dam. You can feed the pigeons and there are always living satues and such around. Here's a pic of de dam
be sure to check all the big shopping streets, and also the smaller one. I know this really dodgy looking store, I think in at the damstraat, where they sell hole patches and patches of all kinds of bands really cheap!
Just have fun, it's a great city!