At the moment the Nationale Strippenkaart is being phased out and will no longer be in use after 19 May 2011. Until then here is an explanation how its to be used.
Soon the Nationale Strippenkaart (strip cards) will no longer be used to pay for public transport in the Netherlands. By May 2011 the OV-chipcard will be the only form of payment accepted.
Until the OV-chipcard replaces it, the Nationale Strippenkaart remains the easiest and least-expensive way to travel on public transportation. Till then, here is an explanation on how the Nationale Strippenkaart works.
Cash to driver
You can pay cash in the exact amount to the driver and you will receive a small ticket as evidence of your journey, but this is the most expensive method.
Strip cards can be purchased from newsagents, tobacconists, some grocery stores and from public transportation desks (HTM in Centraal Station and Hollands Spoor, for example) in quantities of 15 or 45 strips. They are valid for trams and buses everywhere in the Netherlands (except Rotterdam).
Counting the number of zones
The system works like this: you must use one strip as basis tariff, plus one for each zone of your journey, so you'll always use a minimum of two strips. To use the stamping machine, count the correct number of 'strippen', fold your ticket at the bottom of the correct strip, and then insert the card with the fold forwards into the stamping machine until you hear a click. Stamp again for anyone else travelling on the same card. If in doubt about the zones you'll be crossing, they're marked on maps at each of the stops or you can ask the driver.
The maximum number of strips you'll need to stamp is 20, and the tickets are valid only on buses, trams and the metro -- not on trains. However, you may use a strip card to travel by train between stations in The Hague.
Stamping the card
You must stamp the card as soon as you enter the tram or bus. For the RandstadRail, please remember to stamp your card outside at the halt as the RR trains are not equipped with a stamping machine. Trams operate on the honour system but are regularly patrolled by ticket inspectors checking for valid tickets, so always be prepared to show your strip card. If you are caught without a valid ticket, you risk paying a fine.