Manual/Auto Focus, and other settings

I have a real hard time manually focusing with my 20D, so I use auto focus all the time. I usually set the shutter speed based on lens length and let the camera suggest a f-stop, then adjust from there. I also will change the ISO, but I wish it was displayed in the view finder, hate it when I leave it at 800/1600

Manual exposure 90%, Aperture priority 10%
iTTL flash control
AF unless AF cannot focus, then I use manual (thank god for AF-S lenses).

You might want to consider a Katz Eyes split screen if you use manual focus so much.

I usually use AV setting. So far, AF has been able to focus properly. I am sure I will come across with the shots which require the manual focus when AF cannot do the proper focusing.

I'm in Av mode pretty much all the time, and I let the lens do the focusing, unless I'm shooting something with intense backlighting.

I usually shoot in aperture priority and I adjust the ISO as needed, as I don't trust Auto ISO. I normally use autofocus except in certain macro situations, where it is usually necessary to use manual focus.