This Photoshop tutorial via IceFlowStudios is a brief and simple to follow method to make the iris and pupils of the eyes of your model really POP in Photoshop.  We all know we can sometimes use the dodge tool to selectively brighten or highlight the whites of the eyes, but this tutorial focused on the actual iris and pupil.  Using the dodge and burn tools, the tutorial instructor here shows how you can make them really jump out, when you either have catchlights that are uninteresting, or dull; or when the iris is just looking a little bit muddy.

The age old question that everyone asks… Umbrellas vs Softboxes – Digital Photography Tutorial

http://www.layersmagazine.com/comparing-umbrellas-and-softboxes.html/comment-page-1#comment-57050

Sure, you get different catch lights in the eyes with each.  Round ones with umbrellas, square or rectangle shapes reflections with softboxes.  But here the two are reviewed much more in depth by a real studio guru.  A great video by Jean Francois on the Layers Magazine website.