One way I learned what made for a successful stock photo was to read many year’s worth of Shutterstock critique forums. I just read one after another after another and found a generous community of photographers who will give you suggestions about how to improve your photos to get accepted into photography sites. At first the photos the newbies posted looked all right to me, but after a few hundred posts I could look at the photo and predict what the respondents were going to say – that’s when I knew I was ready to submit my photos!
You can see a great example of a photographer who at first was not accepted, then sought advice from the forum, and after acting on their suggestions got in here.
Laurin Rinder and David Smith are particularly helpful, and I got my model and property release templates from Laurin.
Go take a look, you’ll learn a lot!