Public Transport in Amsterdam
You could buy an 'anonymous OV chip card' at the yellow ticket machines at Schiphol Plaza. This costs €7,50 and remains valid for five years. This card can be used on different kind of public transportation systems (tram, bus, train, subway). Make sure that when you're traveling by train, you'll need to have at least €20 credit on the card.
Don't forget to check in and out by swiping your card on the (yellow) card readers. At Schiphol Plaza these are located at the top of the escalators and lifts. If you travel by bus or tram, these card readers are located in the transport vehicles.
Amsterdam Travel Ticket
It's also possible to buy an Amsterdam Travel Ticket with unlimited second class rail travel between Schiphol Amsterdam Airport and any station in Amsterdam for 1 day (€17), 2 days (€22,50) or 3 days (€28). This ticket also included unlimited travel in all buses, trams, metros and ferries operated by GVB. The GVB is taking care of the public transport in Amsterdam.
Single-use smart card (train)
If you're only planning to travel by train from the airport to for example Amsterdam Central Station, it's probably a smarter choice to travel with a single-use smart card.
This costs €1 more than when you're travelling with a prepaid OV chip card, but then you don't need to pay €7,50 for the OV chip card and don't need to have the €20 credit. This can be a pretty good alternative, if you're not planning to use the card more often or if you're travelling with a group.