If you are waitlisted by multiple schools, then its tough to prepare since each school has its own requirements.
I have a friend who was accepted to pharmacy school a few weeks before classes started. Fortunately, she was accepted to her in-state school meaning that the move was much easier than it would have been if she had gotten into an out-of-state school. From what I gathered from her, she just "went with the flow" by just working her behind off getting all the necessary documentation in place.
So, I would prepare by doing stuff that doesn't require a huge commitment of time, resources, or to someone else. For example, you don't want to give a potential roommate a false sense of security and leave them looking for another roommate impromptu should you not make it into pharmacy school. I suppose you could get your shots since you'll have to get them anyway regardless of whether or not you get in this year or the next.
To be frank though, it's rare to be accepted this late so you should worry about this coming academic year and admissions cycle. Getting into pharmacy school now or in August is the figurative cherry on top or gravy.