Hi jjthejetplane,
I know that it's frustrating to be on the waitlist, but congrats on making the list! To start, make sure that you've conveyed your continued enthusiasm to the school by accepting a position on their waitlist, and reaffirming that their school is your top choice. Different programs have different guidelines when it comes to communications with adcom during your waitlist period. If the school offers feedback to waitlisted candidates, I would definitely listen to what they say regarding your application and see if it's something you can address. Sometimes they want a little more work experience, which is out of your control for the current application cycle. However, if it's something like they are concerned about certain skills you may be lacking, there could be online classes you can take to alleviate their concerns. If permitted, keep the school updated on any new progress in your job. Basically you want to provide any additional information to help your candidacy when available, and show continued enthusiasm for the school.
Hope this help and good luck!
Best,
Cindy