Unless you want to make a detailed exploration of the Dutch countryside, you may find it more convenient and less stressful to leave your car behind when touring the Randstad. The region is crossed by a dense network of freeways, but these are frequently clogged with commuter traffic and often grind to a halt at peak times. Avoid the jams by hopping on a train, which is the cheap, convenient, and usually reliable way to get around. Most cities are connected to Amsterdam, and each other, by direct services that run at least twice each hour throughout the day. Rotterdam, The Hague, and Delft have hourly train services to Amsterdam all night.
Taxis are available at railway stations. Alternatively, to get one to pick you up, contact one of the firms recommended by the tourism bureau; you can't hail cabs in the street.
In this flat land, a bicycle is an ideal means of getting around, and cities have safe cycle lanes on busy roads. Bikes can be rented at outlets in practically every Dutch town and often near major railway stations—look for something called a Rijwiel shop or Fietsverhuur. These shops are generally open long hours every day, and the bikes are invariably new and well maintained. Rates run from around €10 per day, and you must show ID and pay a deposit of €50–€150. Be aware that some cheaper bikes have back-pedal brakes and no gears.