General Safety Facts
The Netherlands in general is a safe country, and usually there is nothing to fear when walking in any part of any city. However, the bigger the city, the bigger the chance there is a park or neighborhood you should avoid when the night falls, so wherever you are staying check the local situation. (especially in Amsterdam & Rotterdam)

If you come to Holland with your own car, please take care because a car with foreign registration is a popular target for smash-and-grab theft. Don’t leave important things in the car: remove registration and ID papers and the radio/stereo if possible. Another thing to remember if you are with your bike: make sure to lock you bike with several locks!

Also keep in mind that foreigners are (like everywhere) favorite victims for whoever wants to commit a crime, so try to avoid looking like a tourist/foreigner. For e.g. leave your luggage in the hostel / hotel, only bring a little bag with you to hide your traveler’s identity; try only taking out your camera when you need it otherwise it will be the best proof that you are a traveler.