While workflows are very much a personalised thing there are still some things you should take into consideration in order not to fall into bad habits.
The basic workflow goes like this:
1. RAW Processing
Load your photo into a RAW Processor (eg. Camera RAW, Lightroom, Aperture, Capture One, etc)
Note that these programs are already laid out in such a manner as to improve workflow. As a rule of thumb you should work through the settings from top to bottom.
Once you’ve fine-tuned your picture and you’re contempt, you’re ready to open the picture in Photoshop (or your graphical image editing software of choice).
2. Image alterations
The next step is to create all the image alterations you need. Create a copy of the original layer and go to town! You don’t want to have several layers with fine masks to end up worthless because you decide to do a perspective correction or move some aspects of the image.
Note: With Image alteration I mean any action that will alter the image’s pixels.
This includes the following:
Detail corrections such as sharpening,
Spot-removals and cloning
As large amount of these actions you will have applied during RAW processing though. Whenever possible choose the non-destructive way. Adjustment layers and masks are your best friend!
Only when you’re 100% sure you won’t be doing any other drastic changes to the image’s pixels should you continue with the next step:
3. Color adjustments
Now you start color correcting the image using adjustment layers.
Selective color adjustments,
Vibrance and/or Saturation
4. Image contrast
One of the last steps is composition. Keep in mind The Rule of Thirds as it generally does provide good results.
Depending on what media you want to display your photo on (be it print or screen) you will need to take into consideration the color space and format. If you’re printing you also need to take care in the previous step to make sure it’s the correct aspect ratio and size. Photoshop’s Crop Tool has handy aspect ratio settings for this.
Generally if you are going to publish on the web you will want to convert the color space into sRGB, otherwise you will find that all the colors look washed out and plain wrong.
See also: Color Spaces Explained