What mode is your camera most often in? Why?

I'm not as experienced as some of the posters up the thread, but I think it depends a lot on the lens. I'll use A almost all the time on an f2.0 30mm lens where aperature can make a significant difference, I'm more likely to use S on a superzoom lens at 200mm lens where there aperture's going to be quite slow (large) anyway and I'm more concerned at having a shutter speed fast enough to avoid shake. But I take most of my photos with quite short, quite fast lenses, so I tend more towards A. I use M when I want to make absolutely sure what I'm doing, but I don't like leaving the camera in M in case I need to quickly snap something - leaving it in A or S will almost always guarantee a reasonable exposure.