It's difficult to predict the likelihood of being accepted off of a college's waitlist in any given year. It depends on how many students opt into the waitlist and how many accepted students commit to the college. If a large number of students accept the college's offer of admission, your chances of being accepted off of the waitlist are much slimmer.
However, you can make some estimates based on statistics posted on sites like CollegeData. On the page for Claremont-McKenna College, the latest stats say that of the 349 students who accepted waitlist status, 38 were admitted. That's a bit more than a 10 percent chance of admission from the waitlist. There's no guarantee that this will hold true for you, but it's a reasonable estimate. At Boston College, 2,542 students accepted waitlist offers, and 210 were admitted. That's around an 8 percent chance. As you can see from these numbers, your odds of being accepted off the waitlist are going to be very low at any selective school.
If you want to improve your chances, you'll need to emphasize that the school is your top choice. I found this short article, which I thought had some smart advice for what to do in your situation. The gist of it is this: First, contact the admissions office to see who you should be communicating with as a waitlisted student. When you get the appropriate contact info, write a letter in which you explain why the college is still your first choice, how your ambitions match up with the school, and what personal strengths you have that could contribute to the community. This is the best strategy to demonstrate continued interest in a meaningful, non-annoying way.