Update your application if it's applicable. Any publications? Presentations? Fall semester grades? Significant recent activities or endeavors? Some schools also let you know where you are on a waitlist, and who to contact. I don't think that calling often would help. Once to show interest, or if you are concerned in a couple of months. .but don't overkill. I'll admit I'm not the best one for this advice, since I have not been accepted or on any waitlists and my interviews were recent. But good luck to you!