Nuances of characters

Lately, I have been hearing from my crit group that my characters are sort of pawns of my plot. At first I was sort of like, what about it? They are the characters in my world, so technically they are pawns of my story....

Then I got some more details, and it was a MAJOR defect in my writing, so my writing goal of the newest book is to make my characters more real and in effect make the story more believable. It only took me what, 2 test books. :).

So now I am trying really focus on making my secondary characters little nuances that make them real to the reader, which is what I should have been doing from the get go. Go figure, better late than never and now, thanks to my awesome crit group, I can add another thing that I have improved over the past couple years of writing novels.

What are some of the things that you have added to a character to make them more real and in effect an individual that stands out instead of becoming a 1 dimensional character?