Take every train to Amsterdam South WTC (5 min! first stop), exit here, take tram 5 to Central Station and leave the train at Museum Square (about 10 minutes, opposite to the Concert Building). Walk towards the Rijksmuseum by passing the sqaure (7 minutes, can't miss it) and then to Leidse Plein (10 minutes, Leidse Square). From there to the Canals (3 minutes). Have a lunch on one of the canals, walk along the canals and take tram 5 back to the train station South WTC and a train to Schiphol Airport. The way back will cost you around 45 minutes to be safe. Otherwise send me a "private" mail and I will give you a more detailed program.