As of 2012,
Photography is 70% capturing, 30% editing.
If you don't capture a good photo, editing won't make it better.
Out of that 30% editing, 60% will go into cropping.
Out of that remaining 40%, 50% will go into proper contrast, 20% into brightness, the remaining 30% varies.
Out of that remaining 30% very often, 60% will go for saturation, 20% for vignette, 20% for unknown things.
Note: I didn't consider if your photo is a colored one or black and white. The figures are not accurate. This is just to give you a rough idea.