An anonymous OV-chipkaart has a one-time cost of € 7.50 and can be purchased at sales machines at stations, various tobacco specialty shops (such as Primera), at many supermarkets, at some Bruna's, and at GVB Tickets & Info.
The card is valid for four to five years. Be careful as you will have to check in and out with the card, otherwise a higher amount will be deducted from your card. You can order a personalized card with your picture on it online once you have decided to stay longer.
Get a day card (still paper)
Public Transport Amsterdam: get a day card for €7,50
Public Transport Rotterdam: get a day card €7,-
For transport on the train you can still buy normal tickets at the ticket machines (coins / bankcards / creditcard some)!
The Dutch travel long distances with the bike! You can rent the bikes at all trainstations (ov-fiets), you need to get an membership for €10,- per year though.