Brad Parbs introduces us to the command line, or at least his favorite tools for it. It's a good guide if you aren't yet set in your ways. Though this is for beginners, it's not exactly beginner-ish. So beware.
If I were truly giving a tutorial for beginners, I'd send you to this command line cheat sheet from the folks at Tower, which covers the very, very basics. Which is where you want to start. I still reference this article plenty.
I'd add that I like iTerm2 as a Terminal replacement. It makes things colorful and handles multiple tabs easily.
My number one advice for tackling the command line: baby steps. Baby steps and mentors. Get someone that's a wizard to help you out every now and then, if you have such people available. Slowly, I've started replacing certain workflows with the command line. This is especially so since I now use VVV for local development, and it's handy for some other development tasks as well.