By far the best airport to fly to is Amsterdam's intercontinental airport at Schipol, which is used by main carriers and by several cheap airlines (e.g. easyjet). Schiphol Airport has a rail station immediately beneath the terminal level. From schipol train station, travel to Amsterdam Centraal and change for Amsterdam Amstel. Use the section on trains below for buying tickets, checking times and locating platforms. Use the Google Maps to find your way from Amstel station (first entry in the left pane list) to the conference venue at CWI.
(Other airports used by cheap carriers that are in Holland, or close to its borders, include Eindhoven and Weeze, used by Ryanair, and Rotterdam. All these, and the major Brussels airports, are within reach of Amsterdam by train, but Schiphol is by far the most convenient. Use the excellent site To and From the Airport if you travel to any of these others.)
Use this site to plan your train travel in Holland. The station nearest the conference venue is Amsterdam Amstel, which you will probably reach from any distance by travelling to Amsterdam Centraal and changing; see directions in plane section above.
Some points about buying train tickets in Holland:
This site is only available in Dutch. Select one of the two radio buttons for each of your from and to locations, or select from the 'zoek anders' drop-down list if you want to specific the address otherwise than as an address or train station.
See the Directions to CWI for information on routes that serve the conference venue.