Get your DAT done and request your LORs well before May. I highly recommend getting a committee letter from your science/bio department.
Submit that app before the end of May! Work on your personal statement before the application opens. Allow at least 2 weeks to a month to get the PS done. Write up a draft, let it sit a few days and then open it up again. Revise, let it sit again. Get some opinions from other people, especially professors.
Read up on a few publications about the application process, interviews and personal statements.
Get to know your local dentist and start shadowing! Once you've developed a rapport with him/her, see if they will let you learn some stuff like taking impressions and other stuff that the assistants usually take care of.
It's tempting to apply to only the schools you really want to go to, but you should expand your horizons a bit and include some schools you think you have a shot of getting accepted to (usually private schools in other states). I'd recommend 10 schools at least. Absolutely no fewer than 5, unless you're one of those people who has only one school in mind and only it will do. It takes cajones, but some people do it.