Amsterdam is a city run on bicycles. Bikes and bikers are everywhere. Make sure to look both ways and keep your head up at all times. Spacing out while walking around the city may put a damper on your vacation or a lump on your noggin.
If or when you meander through the red-light district, be wary of people trying to sell you anything on the street. Pickpockets, muggers and thieves alike will use this opportunity to take your money. Just politely say “no thank you” and continue walking confidently away.
The Dutch are very accepting and tolerant people. Some things that may alarm your American sensibilities have been accepted for a long time in Dutch culture. Keep that in mind when wandering the city and try not to allude to people’s differences.