Fridge Quit!

When we open the door to the fridge or top freezer, the light comes on, but neither fridge or freezer is cooling. We had this problem about a month ago. We cleaned all the food out to put it elsewhere, then it suddenly started working again. We thought the problem was a fluke and it was OK, but here we are again. Are there some fairly simple steps I can take to diagnose the problem and possibly repair this beast myself? Thanks!