Smart dodge & burn
I found this technique very helpfull in both of my final images. Creating a new layer filled with 50% grey ( #808080) and set to soft light mode. Using dodge tool for light areas and burn for darker. Very simple.
Adding sulight through the trees – http://www.photoshopessentials.com/photo-effects/sunlight-trees/
I have implemented this technique twice for my ninja image (moon and lamp).
Photo Filter – http://www.surrealpsd.com/ambient-colour-in-photoshop/