GVB (the Amsterdam public transport company operates a netwoerk of night buses in Amsterdam. There are only night buses - trams and metros don't operate after midnight.
On the maps page you can find a link to a map of all night buses operated in Amsterdam.
Most night buses also stop on Central Station.
You can buy a night bus ticket on the bus (with cash only), or you can use your ov-chip card. The price for a night bus ride is E 4.50 (2016).
Night buses go once per hour, so you need to be on time.
The night bus network is less dense than the day buses, so night bus routes tend to be longer and take a bit more time.
GVB bus in front of Central Station