You should buy the book "Understanding Exposure" by Bryan Peterson.
"Going manual" just for the sake of going manual is sort of silly.
There are times and places where manual is the best exposure mode to use. But there also situations where it won't work and either aperture priority, shutter priority, manual with auto ISO or even program would be a better choice.
The best photographers don't use just one mode. They use the mode that's most appropriate for the particular situation they're trying to shoot. You should experiment with each and learn how they work, when each mode has advantages or disadvantages.
When using the auto exposure modes, it's also important to know when and how to use exposure compensation to override the auto settings. What it comes down to is that the built-in reflective metering system of any camera can only do so much. It's got limitations that can cause poor exposures. Exposure compensation is necessary to "correct" some of the "errors" inherent to reflective metering.
There are several ways to do this... which is one of the main topics covered in the Peterson's book. It's far more info than we can ever provide here. (After all, it fills a book!).
Something Peterson doesn't cover is incident light meters. These operate differently than the reflective meter in your camera. An incident meter measures the light falling onto a subject, rather than what's being reflected off of is. This makes incident meters far more accurate, when used correctly. So one of the methods of arriving at accurate exposures is a separate, handheld incident meter.
With experience you also can learn to eyeball exposures. And the image playback an histogram available on most DSLRs is great feedback to confirm your settings.
Quote:
aperture -> (A) mode, F 8, ISO 250 + Auto ISO
Abso-frickin'-lutely NOT!
Manual + auto ISO is not manual. It's just another auto exposure mode.
Any AE mode, such as aperture priority (A or Av) + Auto ISO is piling one form of auto exposure on top of another form of auto exposure. Who knows what you'll get or whether or not it will be possible to accurately tweak it, as is necessary with any AE mode.
My recommendations...
1. If you use Auto ISO at all, use it with M. Just understand that when you do so, M is no longer manual.
2. Never use Auto ISO in conjunction with any AE mode... I cannot imagine any situation where that would serve any purpose.
3. Auto ISO implementation varies a lot depending upon the specific camera. Older models didn't have it at all, of course. Some cameras provide Auto ISO with only a very limited range. Worse, some do not allow you to adjust Exposure Compensation in Auto ISO. To be truly useful, Auto ISO must have upper and lower limit caps that can be set by the user and you absolutely must be able to use Exposure Compensation with it. Any camera lacking E.C., in particular, on Auto ISO, I simply wouldn't use it very much, if at all. There is plenty of adjustability in exposures using the other parameters: aperture and shutter speed.