M.,
It depends on what you want. Your local yarn shops probably offers lessons. JoAnn and Michaels craft stores both have basic how to lessons. If there are some older ladies at your church, in a social group or in your family, I bet one of them crochets and would like to teach you. What about the lady at work that you saw? Most knitters/crocheters love to share their excitement about their craft.
There are some good books out there, if you can learn well from books. That is how I originally learned to knit. I bought a kit called "I can't believe I'm knitting" from Wal Mart and taught myself out of the book. (Warning, it's not the best setup out there. I don't think the book is all that great.) Someone mentioned the "teach yourself visually" series. I have not used them personally, but I have heard really good things about several of the books in that series. You can find it on Amazon used for about $10 here: http://tinyurl.com/crochetbook
There are also tons of good websites out there. The Lion Brand yarn website has tons of free patterns as well as "how to" tutorials for both crochet and knitting. You have to register to see the patterns, but it is free and they won't spam you. They have some nice quality patterns for free there.
If you like videos, you can find learn to crochet DVDs at your local craft store. I have seen them at Michaels, Hobby Lobby and JoAnn. You can also buy them online. Finally, you can look up videos on YouTube for free. There are some very good knitting ones on there, so I bet there are some good crochet ones also.
Best of luck,
S. L