It's now almost spring and if you happen to have a plan to visit Holland between late of March to early May, then don't miss its biggest attraction. The peak of the most famous Dutch agriculture industry: flowers, and especially the tulip bulbs.
The colorful flower fields in Holland cannot be missed, certainly. You may want to visit Keukenhof that opens only in spring and late summer, but the best way to wander around is by riding a bicycle and you can approach these yellow, blue, orange, red and white color of tulip fields personally.
Flower fields are mostly concentrated in the Bollenstreek (the bulb region), which spans from Harleem (south of Amsterdam) to Leiden. I would suggest you to go to Leiden and rent a bike in a bike shop at the train station there. It's only 7 euro for the whole day!! In spring, the bike rental shop usually offers a free small bike route map to go to the Bollenstreek. You can find also other more extended bike route maps in a bookstore at the train station.
So get your gear. A camera with wide angle lens, a polarization filter or just a point-and-shoot camera are well enough to capture these fields. You can stop at Keukenhof to relax and enjoy the beautiful park before continue your journey. Don't forget to bring enough bottle of waters and some snack.