All three of my children have dark brown eyes, and I have the hardest time getting them to look anything but completely flat in pictures. Then if I go in and edit them, they look like alien freaks. (I'll freely admit that I'm not the editing pro - maybe I'm at level .5 on the editing scale of 1-10.) I'd prefer them to look good SOOC, or at least not look completely flat.
This is relatively easy and many great advice has been given. First make sure your exposure is on for the skin tones. Get your subject in a well lit area. This will help in constricting the Pupils . This will allow for maximum eye color to be showing. Get a flash (off camera preferred or bounced of nearby white object) and get some light into the eyes, even if outside. If no flash available and you are outside. Find a nice white wall or tshirt and have the sun hit that and BOUNCE back into their faces.
Thank you to you all. It's just almost crazy to me - I will SEE catchlights and then will see the pic and just get black pools. I'm going to practice on my son I think. His eyes are the lightest of my three, and he's usually a willing subject. The most willing subject basically has black eyes so PS I think is going to have to be my friend there. :)
hope this helps.