M.B.
I have a 3 year old and an 18 month old - this works for both. When they start crying over something little or throwing a fit for something, I have them go to their room until they are done. If you found a spot out of the way (where you don't have to listen), you could have them get it out of their system there. Even the 18 month old will come down the stairs now and say
"cryin'" - which means he's done crying. Now, if I ask my 3 year old if he wants to go to his room, he normally tells me he's done and then goes on to play.