These are some of the adjustments available in Aperture (and I presume LR) that all do similar things... adjust the tones in your images. Are there best practices that dictate which tools to apply to which situations? Are there any good online resources that teach these best practices? Or does everyone learn by trial and error and just moving sliders around until they are happy with the result? Any pointers on where I can get some insights to make this more of a science and less of an experiment in moving sliders would be great.