One of the techniques I use to make the eyes pop in post processing is actually very simple.
I take the lasso tool and select and area bigger than that of the eyes. Next, using the selection, I add a Levels new adjustment layer. Paying attention only to the whites of the eyes and the actual eyes themselves, I bring up the black point slider and bring down the white point slider. When I am done I click ok and take a paint brush on the layer mask, and mask out the overlap. Then I have eyes that really pop.