Bike anywhere, as long as you avoid the center of Leidseplein and Dam Square if you're an inexperienced biker. I would visit the Jordaan in the morning--leave your bike and walk through the small market at Noordermarkt on Saturday mornings, then bike over to Albert Cuyp Straat and take advantage of the market there.
The bike ride I most recommend is one that takes you to Museumplein and then to the Vondelpark. Vondelpark is a beautiful park in Amsterdam, where there are always people walking around, enjoying the lush vegetation, trees, and cool weather. Pickup soccer games take place, rollerbladers do tricks, and couples walk around slowly, taking pause every few steps to look at flowers.
And one of the greatest rewards lies in the center of the VondelPark at the Blauwe TheeHuis--a tea house in the center of the park. It's a blue round bar with outdoor seats where you can sit, chill out, and take a beer or a glass of wine and a small snack. It's a relaxing way to spend an afternoon in Amsterdam, away from the packed Leidseplein, Dam Squares, and Red Light Districts, and a perfect stopping point after going on a bike ride or even seeing the museums. And if it's sunny out, it can't be better. You can enjoy the sun and people-watch--a yuppier scene than some other places in Amsterdam.