tickets for Rijksmuseum and Van Gogh Museum

Online using the hotel computer kiosk the day before works.
Unlike Ann Frank house the museums do not sell out.

I was in Amsterdam the first half of September. Yes, get the Anne Frank museum tickets in advance as soon as they become available. We went to the Van Gogh museum the same day we went to Anne Frank. I wasn't sure when we'd get to Van Gogh. When we got there the line to buy tickets was long. It wasn't so much as that they didn't have tickets, there just was so many people buying them. I didn't have a cell plan, but I noticed when I stood next to the museum I could get their wifi. I then purchased their tickets online and pulled my husband out of the ticket line. I actually told those around him what I did and no one made a move. ??? We had about a 15 minute wait before we could enter the museum. It was wonderful. I didn't go to the Rijksmuseum. Next time.

The Rijksmuseum advance tickets will be for an unspecified date, unlike the Anne Frank House and Van Gogh Museum, which will require you to specify a day and an entry window of either 15 or 30 minutes on that day (can't remember which is the 15-minute one). Suggest you pick a day and time for Van Gogh and then make the reservation when you know.
Ann Frank Huis: this is the one where doing it two months ahead is probably important, if you're going in peak season.

Thanks everyone!