First:
Assess the image
Zoom to 100% and scan the whole image, making note of the adjustments that will be needed.
Second:
Retouching layer
See Non Destructive 101
Third:
Global adjustments
Starting with luminosity & contrast then color & saturation
Contrast will effect how you see your color and saturation
Last:
Selective adjustments
Layer adjustments that are masked off, again, luminosity first then color.
