Jenever (pronounced ye-nei-ver) is very famous and popular in Holland and Flemish speaking region of Belgium.
It has a taste that is similar to Gin, and so people often call it "Dutch gin" when explaining to tourists and foreigners. The drink distilled from malt wine and the taste comes from the 'juniper' berries that grows in Holland.
Is it a great-tasting spirit? well to be honest, no :p but it's the novelty that's important right? Every time I travel I always make sure I try the country's national spirits or drinks :)
There's many different distilleries that produce Jenever in the Netherlands. The famous ones include Bols, Bokma and Ketel One
Jenever gin (also known as Old Tom Gin) is a 16C concoction of distilled alcohol made witha heavy infusion of aromatics (eg juniper berries). It tastes nothing like "Dry Gin" which is a lighter variant made in 1870 and is popularly mixed with fruit juices or vermouth. Jenever is drunk straight and usually chilled. There are 3 grades (of increasing price and smoothness). Outside of Holland it is hard to find. If you are on a KLM flight (their plane and crew, not a shared flight with others) it may still be available. Ask. A little old Dutch lady and I each enjoyed one on my last KLM flight!
Amsterdammers are a very tolerant breed, but they do expect you to behave in the same fashion. It is not a good idea to criticise the way they run things in Holland. The Dutch love to eat herring, either raw or pickled. Try some at one of the many fish stalls on the side of the street. The many cafes are a great place to relax for a while on a rainy day, and to sample Dutch gin, the national drink (ask for a Jenever). Smoking is widespread in Amsterdam, with very few non-smoking areas, so again, be tolerant of this. Marijuana smoking is illegal outside of 'smoking coffee shops'.