We stayed a week in Amsterdam before our Viking River Cruise.
But we did a lot research beforehand on what we wanted to see and do and then scheduled it out per day and it penciled in as 5 days. We flew in, the next day is jet lag day, where we do nothing but rest if needed and to take walks around the town.
With our itinineary planned out, we saw what we wanted to see and do, but wish we could have stayed longer.
We stayed in two places: in a houseboat in the Jordaan neighborhood and then at the Doubletree Hotel near the Viking River cruise port and walkable from Amsterdam Central train station.
We really recommend finding lodgings in the Jordaan neighborhood. Don't stay in the Red Light District, but definitely walk through during the day. The museum district also has nice hotels.
Read the other posts in this forum for ideas on what to do. What are your interests? only you can determine if it's something you want to do. In addition to the Rijksmusuem, the Van Gogh Museum, the Dutch Resistance Museum, the Maritime Museum, we visited the Anne Frank Huis, took an evening canal tour with those Damn Boat Guys, had a Riffstafel Indonesian dinner. We took walking tours of the Central area, and a walking tour of the Red Light District, with the PIC. We rented bicycles in Vondelpark and spent a morning riding around the park. WE visited the Albert Cuyp open air market and and sampled the local food. If you haven't done any research on what food to try, then take a food tour. We also bought our orange shirts for Kings day and souvenirs.
We took day trips to Giethoorn, Harlem and Delft. Since we went in April, we visited the tulips in Keukenhof.
That's what we did, but you do you.