Tip - One Key to Success is Diversification
"Don't put all of your eggs in one basket" is an old saying that rings true with micro stock photography. At least in my limited experience.
Basically there are two schools of thought when it comes to your portfolio:
One is that you should concentrate on what you like to photograph. If you like taking pictures of trains or flowers or the stars, then develop a stunning portfolio that covers the subject from all angles. The only downfall of this is if your subject matter is not in demand of potential buyers.
This strategy is appealing to those who really love a certain subject and use photography to express this love. But in the end you might have the most amazing portfolio of 500 images of paper clips (if that's what gets your creative juices flowing) but there might only be six buyers looking for paper clips.
The second school of thought is to create a diversified portfolio of many subjects that will appeal to a wide range of potential buyers. I think this strategy appeals to people who have a love of photography and will take on any subject as a challenge to bring their talents and creativity to that subject.
It takes a lot of thought and skill to create new ways of looking at subjects that have been done to death or are inherently boring. But somehow good photographers can take a boring everyday object and bring it to life and make the viewer see it in a whole new way.
Either approach is valid. Concentrating on one subject that you love is sure to bring about some amazing photographs although it might not lead to many sales.
Diversifying and covering a variety of subjects is my strategy and it has led me to a level of success in a short amount of time while seeing some of my peers becoming frustrated that their sales are not forthcoming from their narrowly focused portfolio.
Keep in mind that the designers do not stick to single subjects. The designs they work on come from the variety of clients they serve and they never know what kind of image they will need next. By provides a wide range of images and subjects, it ensures that your portfolio has a chance at being used.
These images are my most recent sales and give an indication of how diverse my portfolio is at this point:
Photo credits: Peanutroaster.