All these schools have large waitlists and take relatively few from them in most years. So the statistical odds of moving off the waitlist is smaller than the original odds of getting in. It can and does happen, but the odds are long. the higher a schools yield, the worse the odds get and Pomona has one of the highest yields of all the LAC’s. Also, depending on the year you might have to be in limbo until as late as July to find out if you got off the waitlist or is is closed. In the meantime you will have to accept somewhere else and pay a non-refundable fee, etc…
In terms of strategy, people have tried all sorts of things ranging from a passionate letter about their ongoing interest to traveling to the school to show up and say it in person or finding an alumni to write a letter to asking their high school college counselor to call and make a case for you. There’s no reliable info on whether any of this helps and with the very competitive schools my guess is most of it doesn’t – beyond a simple letter of ongoing interest.