Ask.

Ok, it is a little more involved than that, but not much. The key is to make it easy for your clients to help you out. If they can write a review or two in a couple of minutes , they are likely to do it.

Be sure to have a few places set up for them to write reviews, then send your clients an email after their portraits or events.  Email is key because the links are hyper-linked, requiring only a click. The letter could look something like this:

Hey “Awesome Client”

I just created some online profiles and really need your help.
If you’re super happy with the work we did for you, please consider writing an online review for my studio.
This will help other people in search of great images.

Below are a few places where we are listed. Please pick one or two a write a quick review.
Yelp,  Google, Yahoo, ETC, ETC, ETC

It only takes a few minutes, and Karma is a wonderful thing.

You Rock, we can’t wait to get you back in the studio!
Zack Wessels, Photographer