Lots of good suggestions from the CiC forum members. They all encourage you to experiment, which really is the best way to learn. Consider trying this:
1. Set camera on iso 100, which is where it should be unless you have a specific reason to change it.All I have done here is to describe an experiment to allow you to see what effect making changes on the camera has on the photos. What I do in real life is look at the histogram the camera shows me, which helps me understand how under/over exposed each shot is. After a while you just "get a feeling" for how to bias - I usually work in Av mode.
2. Get yourself a notepad and a pencil.
3. Sit down somewhere comfortable, with the camera pointing at something that interests you, maybe a landscape?
4. Put the camera in a fully auto mode and take a photo. Note the aperture and shutter speed, and write these down together with the filename of the photo you just took.
--> Here we are letting the camera decide what the photo is of, and use all it's clever software to work out what shutter and aperture to use.
5. Put the camera into manual mode. Either dial in the aperture and shutter speed the camera just used in auto mode, or use the "sunny 16 rule" which says that on a sunny day, using a shutter speed of 1/100th sec you need an aperture of f/16. (In the UK where it's never sunny, I usually use the not-so-sunny 8 rule, and use f/8.) These are just two ways to get a roughly the right exposure. Now take a photo of the same scene as before, and jot down all the numbers again. If you chose the same settings as the camera did in auto, then you should get the same sort of photo. If you dialed in f16 and 1/100th perhaps the scene is underexposed (too dark).
--> Note that in manual the meter reading is not used at all - you are making the decision about how to take the exposure. Therefore it doesn't matter what metering mode is selected.
6. Now vary the shutter speed. If you used 1/100th before, try varying between 1/25th to 1/400th. (That's four times the shutter speed, to one quarter of the shutter speed.) Take lots of photos along the way.
7. Put the shutter speed back to 1/100th, and now vary the aperture from F/4 to F/32. Take more photos.
--> When you review your photos on the computer, looks for depth of field effects. How much of the shot is in focus?
8. Have a cup of coffee because this might be getting tedious!
9. Now try exposure biasing in Av mode. Put the camera into Av, and dial in the settings that you used for aperture at step 5. Provided the sun hasn't set, the camera ought to select the shutter speed it used when in auto mode, or thereabouts. The camera is now using meter readings. Take a shot and note the setting down again.
--> This is the thing that I remember as the biggest aha! moment when I was learning. The meter reading shouldn't be trusted. Just because the camera thinks it knows what exposure to use, it's not really got much of a clue. It's really just guessing. It's assuming that the camera is pointed at an "18% reflector" like concrete, grass, human skin or sky. It might or might not be.
10. Now that the camera has suggested a shutter speed to us, we are free to change it. In Av mode you change the shutter speed by dialing in a exposure bias. The bias is set in plus or minus stops, typically with 1/3 stops along the way. Take some shots from -2 to +2 exposure bias. Note down the aperture and shutter speed and also, this time, the bias you dial in.
--> You should quickly find that a photo with F/16 and shutter speed of 1/100th, with an exposure bias of -1 is taken with a shutter speed of 1/200th. An exposure bias of +1 results in a shutter speed of 1/50th. Adding or subtracting a stop halves or doubles the exposure time in Av mode.
Hope some of this is helpful. Don't feel you have to laboriously go through these steps, and certainly not all at once.