just dive in/take the plunge and make a scarf (that you'll probably never use or give to your dog) . . . and then practice a row of single crochet and then work up to double crochet. it probably won't be parallel on the sides, but it's a good starting point to get comfortable with the tension. just don't get toooo small of a crocket hook to start/practice. i think a J is a good size/you can see your stitches.
the hardest part is holding the yarn/getting your hands in the right position . . . utube videos are great like the others said.
also start asking around . . . i'm sure you'll find someone at a senior center that knows how and would love to show you.
edit . . . once you've mastered a square, then you can go onto bigger & better things . . . like a circle!
edit . . . and you can just use your fingers & yarn . . . http://www.youtube.com/watch?v=6FeEEWiA_kY