Digerati University has asked Matt LeClair, the author of Photoshop in a Nutshell to contribute a pretty good article on some basic image editing. He introduces 8 steps, from crop, rotate and scale to improve sharpness. The step on fixing color and contrast using Curves tool is probably the single most important thing to edit any photos. Some of its readers mentioned about saving the scaling till the last step. I agree with them because the unscaled image should give you higher resolution to work on the details:

  1. Crop, Rotate & Scale
  2. Fix Scratches & Dust using the Clone Tool
  3. Expand the Tonal Range using Levels
  4. Add Contrast using Curves
  5. Adjust Midtones using Curves
  6. Adjust Color using Curves
  7. Improve Sharpness using Unsharp Mask
  8. Compare

The 8 Basic Steps of Image Editing – [Digerati Unversity]