Don’t cycle in the city center. I know that a lot of people want to try cycling in the city but unless you are a professional its so hard to cycle in the city. You have to be very alert, and able to focus on everything around you. The cars, scooters, people, other cycles; it can be a little overwhelming for a beginner. If you are excited about the cycling and want to try renting a bike, there are plenty of areas which are much quieter than downtown, parks and neighborhoods which are perfect for a casual ride.
Avoid buying drugs on the street. This may seem obvious, but a lot of tourists come to Amsterdam looking to experiment with drugs and make the mistake of using poor quality products, unfortunately ending up with severe health problems. If you want to try drugs you can visit a smartshop, where the staff can provide you with the information you need before buying anything, and is also much safer as the drugs that they sell at the shop are regulated.