Thanks very much Karifan! My secret recipe involves lots of playing around in Photoshop till it looks ok. I mainly use curves, and I usually start in rgb colour, but transfer to lab colour to get it just right. Shadow/highlight is helpful too. I almost always 'unsharp mask' it first, as to do it afterwards would take away from the effect a bit. (I think!)
Basically, I love messing around in Photoshop. Most of the time I mess around too much until it looks rubbish, but sometimes I am lucky!