I used to believe in ghosts. I had the Little Giant Book of Ghost Stories, or something like that, and I particularly remember the Mothman story for whatever reason. I loved reading that book right before going to bed.
I used to think Sylvia Browne's shtick was real; I think it was mostly because of the ghosts.
In 7th grade (that's 12 or 13 years old), I did a research report on palmistry and I basically bought into it. Mostly, though, I got some exposure to internet censorship, as almost every website I tried to get access to was blocked for being occult.
So, those are my crimes against skepticism, but I grew and now I know that none of that is real. Except for schools blocking websites; I run into that several times a day.
As they say in programming: garbage in garbage out. Most of the misconceptions I had; were the result of being given inaccurate information. Almost all of my early sources of information were insane, my father, the nuns, etc. so I began life with a boatload of crap that I had to eliminate before I could get to the point that I could actually rationally analyze the information that remained.
When I was a kid, I used to believe that I only needed to breathe when I felt like it. I certainly remember breathing except when I was paying attention to it. I would upset me no end when I couldn't just stop breathing whenever I wanted.