Here is a stratagem that I was told worked to get one off the waiting list, at least in the old days, at least for law and MBA programs. I do not know if it actually worked then (but it makes sense) or if it still works now.
Show up on the day everyone reports. At least for MBA and law programs, which have at least 100 students in a class, someone ( perhaps many someones) who said he was coming changes his mind and does not show. (He forfeits his deposit.) Maybe he said he was coming and got in at the last minute off the waitlist to a school he preferred. Or may be he decided to spend the year surfing. Who knows?
The admissions office has a problem. It wants to fill the class. If you are on the wait list, you are qualified. Do you think the admissions office wants to spend the day frantically calling the number one guy on the wait list, the number two.
When someone steps up and says, I am on the wait list and I am here now, ready to go, what do you think the admissions personnel are going to say. No, you are 23rd on the list. We want to frantically hunt for number one and two. No, you are there. Their problem is solved. You are in.
(This might work less well in this age of cell phones, but the logic is still pretty good.)