Here's a secret for all of you who are frustrated trying to learn manual mode. ...it took me at least 3 REAL tries (in addition to numerous half-hearted attempts) before I learned how to use manual mode. Know how I finally did it? I tackled it one piece at a time. I limited my reading to what the numbers meant for aperture and shutter speed and with the aim that all I cared about was how the different aperture settings would effect my photos, and what shutter speeds would be fast enough so I didn't need a tripod. And I wrote down short notes to help me when I had my camera in hand:
small numbers = shallow depth of field = more light
large numbers = deep depth of field = less light
60mm or less = minimum of 1/60th
over 60mm = 1/lens (100mm = 1/100, 500mm - 1/500, etc)
That's it -that note and your camera's manual are all you need for your first outing. Put your camera on Aperture Priority mode, go outside during the day when there's a lot of light, and practice on anything you can find. Aperture Priority mode is great -all you do is set the aperture you want, the camera will find the shutter speed to match it, so as long as the shutter speed is fast enough (according to the note above), you're fine -shoot away! If the shutter speed is not fast enough, increase your ISO.
With time you'll get a feel for how aperture effects your photos, how your shutter speed changes when you change the aperture, and how ISO effects your settings as well. It's a great, slow way to learn.
When you're comfortable with aperture, explore other people's photos and find things to experiment with as far as shutter speed goes -there's light painting, silky/milky waterfall effects, ghost effects, etc that involve shutter speed. The more you experiment, the more you'll learn.
This slow way of learning by doing worked much better than reading and studying for me because there's just so much to learn at the beginning. You can read and understand 10 pages of material, but when you pick up the camera it all seems to blur while you try to figure out which of those numbers are what setting, and which buttons and dials effect what. Learning one thing at a time, slowly, worked much better for me. If you're frustrated trying to learn manual mode and feeling overwhelmed, this way of learning may work better for you as well.