I use 'em all to be sure I get my money's worth.

Probably at least 80% is "A" mode, matrix metering and "S" autofocus mode (Nikon terminology). Knowing when the camera can't give me the results in those settings is really the most important thing. That's when I'll probably use manual exposure and/or focus, and maybe a different metering pattern. It comes from experience with a particular camera, but this is a very valuable thing to learn.

Actually I don't use "P" and very rarely use "S". Nothing wrong with either, just not how I shoot. "P" will do a great job in a lot of situations and I probably would be wise to use it more often.