Manual Settings This is quickly becoming my favorite shooting mode as long as the lighting is even and not constantly changing. I try for an aperture of F8 to as wide open as possible depending on how close the subject is. And the shutter no slower than 750th of a second, the faster the shutter the better. Unless you are going for motion blur and panning then a 30th or 60th of a second can give some fun results. I try to keep the ISO as low as possible like 200 or maybe 400.
The secret to using manual is to keep an eye on the needle on your Canon camera viewfinder. If it is in the middle your exposure should be 'right on'. Changing either the aperture, shutter or ISO will move the needle either to the right of middle which will lighten your image or to the left of middle to darken your image.
Aperture Priority (AV) I still like this mode a bit more than using a manual setting. Sadly I must admit I very often forget to look at the needle in my viewfinder when in manual. Then especially with wildlife you'll miss a great shot because you haven't changed your settings when you've gone into a forest after being in a wide open meadow.
So with that being said I like shooting in AV priority mode with an aperture wide open like at 4 or 5.6 as long as I have plenty of light. I again try to keep the ISO as low as possible like 200 or 400 to get fast shutter speeds. With those wide open apertures you get that great background blurring and sharp subjects that you have locked your focus on.
Shutter Priority (TV) I will use TV when the light has gotten very dim and I can't trust AV to stop the action enough to keep the blurring under control. Try to steady the camera if you aren't using a tripod or monopod by leaning against something. Depending on how fast your subject moves a 500th should work if the subject isn't a real fast mover. If you are trying to shot a bird or galloping horse a 1,000th is really needed to get a sharp image if you are steady. What you will find in TV is you might be getting shots but they will be very dark. To avoid this you can either set your ISO higher or even try the automatic ISO setting. I never used this automatic ISO setting as I didn't want my camera to be shooting at one of those astronomical ISO settings. But since I've upgraded my Canon 7D with the new firmware that I blogged about earlier I was able to set the maximum ISO to an acceptable level. I still like to set my own ISO but that is always subject to change, I never thought I would like to shoot in manual mode either. So I never say never.
And always, always check your LCD often no matter what mode you shoot in to see if you are getting the results you want.
AND ONE LAST TIP: I never ever believed all those photographers who said 'Turn off the image stabilization when shooting fast moving action in the burst mode'. I really thought they were crazy. I fought this for a long time until I tried it.....the results were many more images in focus than ever before.
Remember, I'm by no means an expert at this but I keep on working at it. Some of it might be helpful in finding your photographic road.