1) The game isn't over until it's over. This is traditionally somewhat of a lull period in admissions as most or all acceptances have gone out at this point, making the class lists "saturated." Things will start speed up once people begin making their decisions and withdrawing from schools. Revisit weekends will also be happening over the next month or so, which again supports movement on the class rosters. If you haven't received an acceptance by May 15 - even though you may be on multiple waitlists - I would begin working on your application for your next cycle. But don't simply fill in the application again with the same information. Make sure that you've actually taken some time to reflect and make changes to improve your app. If you don't do that, don't expect anything different next year.
2) As said above, just about the best thing you can do at this point is send update letters to any schools you interviewed at (if they accept them). Tell them about what you've been up to, your fall grades (assuming they're good), any extracurricular or academic achievements, and maybe a line or two emphasizing your interest in the school and why you want to be a student there. Other than that, there's not much to do other than wait.