I'll reinforce what Mike has said, you do not need experience as a basic before Paramedic. I know a lot of programs require it though, which I disagree with but can't change, so check with the program you're looking at.
I don't agree with volunteering though. I volunteer as an RN in a low-cost clinic 5 days a month and one out of 6 physicians are paid, the rest volunteer their time as do 2 dentists. Volunteering can be a great way to give back to your community and gain experience. I started when I was 16 as a volunteer and it was a great way for me to obtain my basic and learn the way EMS works, I had to wait until 18 though to take paramedic because of National Registry, but Maryland doesn't require NR for basics so I could get it at 16.