Traveling to Amsterdam
Amsterdam can be easily reached by airplane; Schiphol is a large international airport. Inside of Schiphol there is a train station with many trains going to Amsterdam Centraal Station.
Alternatively, Amsterdam can be reached by train directly from several large European cities, such as Brussels, Paris and Hannover.
For those traveling from the ICA 2019 conference in Aachen we recommend going by train: Transport from Aachen to Amsterdam
Traveling within Amsterdam
This webite gives a good overview on how to use and pay for public transport. It can be summarised as follows:
The standard method of paying for public transportation is using a public transport chip card (OV-chipkaart), which can be charged with credit and is valid on all trains, trams, metros and buses. Traveling on credit with a chip card is generally cheaper than buying disposable paper tickets, especially for short rides, but buying an anonymous plastic chip card, available from ticket machines on all train stations, does cost €7.50 (excluding credit). Also, the card needs to be charged with at least €4 to start any bus, tram or metro trip, and €20 to start a train journey. They are therefore not always practical for short visits.
If you only need public transport a few times, it might be cheaper to buy disposable paper tickets. In the tram and bus, these can be bought from the driver for €3 using your debit card or credit card and are valid for one hour. For metro, they can be purchased from ticket machines that are available on every metro station.
A third option would be to buy a day pass or multiple-day pass that allow for unlimited travel. This for example allows for travel in trams, buses and metros (by GVB, which includes most lines), this includes all methods of transportation, i.e. trains as well.
Lastly, Uber or standard taxis are widely available in the city.