I do it different each time, but these are the basic steps:
1. Create a vignette by using the lassoo tool and selecting a area about 1/4 from the edge of the image, invert the selection, feather to 100-150 pixels (my images are 8 megapixels).
2. Create a levels layer and move the mid-tones to about -0.5
3. Add a curves layer and increase the saturations/contrast with an s-curve.
4. Add a new layer, fill with black, then set the blend mode to Hue and opactity to 20%-40%.
5. Sharpen.