when i was a kid, i learned through a class at the big fabric store in town. i'm a classroom-learner, so it was perfect for me. my mom also taught me a lot and i would learn by doing as well. if i wanted to be a ______ for halloween, i would get the pattern and fabric and my mom would help me if i needed it.
recently, i've taken lessons at a great place in san francisco called stitch lounge. it helped me a lot! if you're the type of person that works well in a structured environment, it's a really helpful way to learn. most sewing class places have machines, too, so you can figure out if it's really a hobby you want to pick up without spending a bunch of money on a machine.
i also definitely recommend just trying. start with patterns that say "easy." some people start without patterns, but i'm hopeless without everything being spelled out for me. if a friend has a machine, just bring some scrap fabric over and play around with his/her machine. there's a bunch of great books, my favorite is by the same people i took classes from. they're all about reconstructing clothing and starting with the basics:http://www.amazon.com/Sew-Subversive-Dirty-Fabulous-Fashionista/dp/1561588091
hope this helps!