I'm planning on putting a deposit down at School A in the next few weeks, but want to stay on the waitlists at some other schools.

From past applicants, I've heard that schools often instruct you to get back to them with a reply quickly (e.g., "tell us by Monday") if they accept you off of their waitlist. Let's say that I get admitted to School B off of its waitlist in May, and I like School B more than School A, so I say yes. Do I have to withdraw my applications from the other waitlist schools?

And if I then get admitted to School C, which I prefer to B, off of their waitlist in July, may I withdraw from School B, or am I now bound to School B?

Are you starting to sketch a diagram as if this were an LSAT question? Me too! Once you're finished sketching, the happy news: No, you are not bound to School B.

Here's the rule to apply: Unless you were accepted through a binding Early Decision program (in which case you would have had to withdraw everywhere else by now anyway), there's no obligation to withdraw from any waitlists after you have accepted any offer.

You do risk losing your deposit after you've put one down, but afterwards you are still always free to stay on waitlists elsewhere and accept an offer from a waitlist school. Nothing is binding just because you put down a deposit, whether your spot comes from the regular pool or from the waitlist pool. The deposit is basically the fee you pay to take your spot off the market and have it held for you; you're still allowed to wait for other decisions to come in. So as long as you weren't accepted to School A through an Early Decision option, you are free to stay on as many waitlists as you like and see what happens. And if all the stars align for you, that means you'll put down your deposit at School A, then receive and accept an offer from School B, and then receive and accept an offer from School C. Sweet!

Schools frown on the practice of holding more than one seat via multiple deposits, though, so if you accept an offer from School B, you'd be expected to withdraw from School A. And if you subsequently accept an offer from School C, you'd be expected to withdraw from School B. That frees up those seats at Schools A and B respectively to be awarded to other waitlisted applicants, who will also be having a very good day.

Good rule to remember: you should have only one deposit at one school at any given time.