The best tutorial for drawing? Practice!
Working on your basic shapes, understanding lighting, and drawing what you see (not what you think that you see) can honestly get you pretty far.
For starting out, I would personally recommend for you to check out Andrew Loomis's "Fun with a pencil". It's a nice beginner book that will allow you to view things, such as human faces, in shapes and basic structures. From there, check out some of his other books as well. In addition to Loomis, other masters such as Hogarth or Bridgman could prove to be beneficial for you. Just do some quick searches around and you'll find a lot of resources.
With regards to art classes, in most cases it's well worth it. Will it determine whether or not you become proficient? No. There are many professional artists that have little to no formal educational background. If you're sincerely interested in this subject and would like to learn more about techniques, as well as other things, then it likely would be worth it for you to attend classes.