This was previously posted on the sigma thread, but i guess its a good to share it with you guys too.
So here's the read.
This is what most ppl will do. Not much editing but with good results. I used an image of a forumer here for an example.
1st, To give it a little kick, boost the contrast. Go to photoshop > Layers > new adjustment layer > curves. Apply an "S" curves to the image. Like the picture below(pay attention to the points that i placed, You can increase the effects by applying a deeper S curve):
Then use Levels. Go to photoshop > Layers > new adjustment layer > levels. See the picture for example:
Here I pulled the highlights slider, which is on the right, just about near the inner end of the slope of the histogram "mountain". This will increase the highlights of the whole image. Then i go to the left side of the slider, which is the slider to tweak the shadows, i pulled it in a little, like what i did for the highlights, but different direction. Lastly I go to the middle slider, which is for the midtones, to darken the image by a little bit. The default value for this is 1.0, but I set it to 0.9, based on my liking.
You can use the preview button to see the before and after effects of the whole image. once you're done on every step, press ok.
That should add a little extra kick to the whole image. Make sure that you dont blow the highlights when you tweak the slider for the highlights. Here's my results:
Before:
After:
Hope this helps.
p.s: this is also what some of the photographers call the "velvia look". Colors which are almost as the same from Fujifilm's Velvia series film. Which produce saturated colors with a whole lot of kick.