1) My #1 Microstock Secret - look for things that other people DO NOT shoot, that buyers might want. Copying best sellers is like getting to the dock after the boat left, or closing the gate after the horses have escaped. Sorry, copying and chasing isn't the answer.
2) Don't pay attention to the little man behind the curtain. Which means, don't search your searches, don't watch the pot, don't check your placement every day, it doesn't change anything and will make you crazy! How many views before something gets a sale is just as much a waste of time. How many photos before you get a sale or steady sales? All that matters is What is the image of! Someone with 200 really appropriate, good concept photos will outsell someone with 3000 uninspired, dupes of inch by inch, repeating themes. It's not how many, it's what's in them!
3) Don't give away your real secrets on an Internet forum. There are probably 80-90% lurkers here who hardly ever write anything and are just absorbing all the wisdom of the rest of the people. Just like the copiers, who re-shoot best sellers for their collection, they also thrive on fresh information. Everything you write here is helping eight other people, take away some of your sales.