What I love most about King's Day is the free flea market around the whole city & orange dress code. It is literally a huge party in the Netherlands.
It usually lasts from 6.00 till 21.00.
I would suggest:
1. dress something in orange - glasses, hat, t-shirt... or you can buy them from HEMA.
2. get some cash for the open market as people gonna sell "anything" they want on the streets.
3. bring some drinks as it's true energy consuming!
4. make sure your phone has enough battery to take photos or videos.
I was there two days ago. It’s a city but with a town-relaxing vibe. There’s a river around the city town. The town is both historical and clean, well organized. You’ll find beautiful architecture and nice stores.
In a word, it’s truly a great destination for short or long stay. And easy to get around by car or train.
My favorite in Amsterdam!
See the route on my Google Maps