5. Sleeping in too long on a sunny Saturday or Sunday
Skipping the nice weather would be your first mistake, which you'd regret one rainy week later. When the sky is blue, whether you're headed to a terrace or the park, you'd best carve out your territory early, because once everyone's sitting, no one's moving until the sun goes down.
6. Buying any drugs offered to you on the street
Hard drugs are not legal, regulated, or supervised in the Netherlands, and tourists have died from buying the wrong stuff.
7. Getting a multi-speed, second-hand bike
It'll be fun for a week, switching back and forth between the gears on the few steep bridges where it's kinda useful. Until the whole system inevitably (and swiftly) breaks down, leaving you stranded in impossible-to-pedal fifth... until the day your bike is stolen by a junkie and sold to an unsuspecting noob on a bridge near the Red Light District for €15.