While you could well purchase daily and weekly transit passes, the easiest payment method to get around on mass transit is the ‘OV-Chipkaart’. Given a wide range of transit companies accept it, it will connect you across the country with ease. You have two options: Get a blue "anonymous" card (one that is not tied to a specific person, useful if you plan to share it with others) at train stations, tobacconists or supermarkets. Or to get the maximum value, get a yellow "personal" card, available online at www.ov-chipkaart.nl, with which you can subscribe to annually renewable discount offerings with your favoured transit companies.
Machines to top up your credit are located at train stations, our ubiquitous Albert Heijn grocery stores and more. U-OV is one of Utrecht’s regional bus and tram system, while NS is the national train system, with both local and intercity lines. If you have an OV-Chipkaart, it can also be used for U-OV vehicles. Note that they are unrelated entities, as the OV-Chipkaart serves as credit for fares on a wide range of domestic transit systems. Visit here to learn all about the U-OV system and to plan your first journey!