I just got into astronomy about a year and a half ago, and my parents are worried I'm getting too serious about a career path too soon. Then again, they're both geologists--I got so sick of looking at the earth I decided to look elsewhere. I don't know what my parents did to get me so hooked, but I think it was their interest in science that got me started, and after that it was the magic of me discovering my passion on my own. My parents think that, even in high school, I'm too young to know that I want to be an astronomer if I grow up.
Honestly though, I have to say the biggest science turn-ons for me a few years ago were Bill Nye the Science Guy and I will never forget the incident in fifth grade when a kid in my class clipped his braces into a light bulb circuit (you know the kind with the alligator clips, 9-volt battery, and mini light-bulb?) Little cool things like that that never happened while studying grammar...
Unfortunately though, I've got to say that a lot of it has to be self-discovery. My parents taught me too much about Geology too early, and I haven't been interested in that since I was about six.