Hi Sharon; I'll be in Amsterdam at the end of April myself. Everything I've read about Anne Franke Museum/House is there are three ways to get tickets. One is waiting in the long ques, another go late in the afternoon or early evening when the ques are short, they stay open until 10 PM. The third and highly recommended is of course to make reservations. The problem with making reservations it is hit and misses. It seems they only release a certain amount of tickets each day and when those are gone that is it for the time being. They will eventually release more tickets through the days and weeks before. This web site http://www.annefrank.org/en/Museum/Practical-information/Online-ticket-sales/. I just checked and for May and the following are the dates they have a few tickets for, May 3, 5, 8, 11, 19, 21. It is not 11:25 PM CST, so I don't know how much longer these will be available.
On May 1st the museum will start a new policy; the only way to buy the museum from 9:00 AM to 3:30 PM is those who purchase their tickets online. The ques will open up at 3:30. This may help you; it seems logically that since they cut the number of tickets to purchase in the queue there would be more to sell online.
If you don't get ticket after you first search, don't give up; as I mentioned they will periodically add more tickets. I started looking for tickets about 3 or 4 week ago; nothing, absolute nothing in April, May, and on into June. I'd monitor their web page periodically and every once in awhile I' come across some dates tickets could be purchased online. Than 3/26 there were several days with online tickets available.
Sometime they have a 30 Intro program available when you purchase your ticket. I've been told if it is open go to; it is well worth the extra $5.00 you are charged.