I subbed for a class that was talking about Fact vs. Opinion. It just happened to be a science/social studies class. Anyway, every Tuesday each child gets a local newspaper. They take them home and read them with parents and what not.
So, for that day, I handed everyone their paper and a sheet of paper. We folded the sheet in half and on one side they wrote the word Fact and on the other they wrote the word Opinion. Then (in groups or 2 or 3) I had them search through the paper looking for examples of Facts and Opinions. If I had more time to plan, I would have let them cut out their examples, but I just had them write enough so that when I asked for examples later, they could tell me.
I was AMAZED at the things they thought of and found. My favorite was the weather forcast. Is it fact or opinion? I told them as long as they could support their answer, that I would accept most answers. When the regular classroom teacher returned he seemed to like the idea.
We also discussed that a fact is something you can prove while an opinion is something that someone could "argue" with. Then I tell them to try and "argue" the statement in their head before they make their choice.
John's shirt is blue. (Really hard for them to argue that)
John's shirt is the most beautiful in the class. ("Well, I think Tim's shirt is beautiful. I don't like the shade of John's shirt.")