I'm an EMT in NJ. Basically, just go to your local office/hq/corps./whatever they call it, and talk to someone. They'll inform you of when/where classes are, etc.
There's lots pluses to being EMS. It's good skills to know, it's fun/exciting at times, etc.
Now, there's also special perks.

Each hour that you're on call counts as a volunteer hour... I actually got a scholarship because of all my volunteer hours. You get a permit for lights on your car. Since I became an EMT, I have not recieved a traffic ticket (they might give you a no-seatbelt no-point ticket). If I get pulled over, I hand him my license, insurance, registration, and EMT ID.
Oh, and there's special perks, too. Verizon Wireless is 15% off for EMS. 2 years ago we had free passes to Disneyworld. Last summer we had unlim buy-1-get-1-free passes to Six Flags, etc.
All in all, it's a rewarding experience, it provides you with good medical training, and it's exciting and fun.