The Secret of Microstock - It ain't so secret
For those just discovering the world of micro-stock photograph and turning your photographs into earnings, there is a steep learning curve. You have to learn how to step up your technical game taking pictures and developing them with software like Photoshop and/or Lightroom.
You have to learn how to develop your eye for the types of photographs micro-stock buyers are looking for and you have to have the determination to continually learn and improve while being patient enough to allow your portfolio to grow to significant size - and then the sales will come.
The good news is that the secrets of success are not all that secret. Hard work, creativity, imagination, investment in good quality tools and determination are required.
All the "secrets" of getting model releases, photograph ideas, technical issues are available within the forums of the Dreamstime and other stock agency web sites in the form of FAQs, message boards and most importantly in the portfolios of successful photographers.
Books like "Taking Stock" by Rob Sylan (http://www.takingstockphoto.com/) and others give an overview of the stock photography industry.
Blogs like Making Money With Your Camera (http://makingmoneywithyourcamera.blogspot.com/) share tips to microstock photographers.
The Dreamstime community is a valuable resource for any photographer starting and your fellow photographers are very supportive of each other but don't expect to take short cuts to success by being lazy and not putting in the work needed to learn this business from the free resources available. Don't ask things like "what photographs sell" or "what should I shoot" - look around the database and find out what sells and figure out what you like to shoot. If there is a motto around here it is "Keep shooting and keep uploading".
FYI - Wisconsinart had a great reality check blog a while back: https://blog.dreamstime.com/2011/09/10/you-can-lead-a-horse-to-water-but-you-can-t-beat-any-sense-into-it_art36108
Photo credits: Peanutroaster.