There are some pretty awesome "Thankfulness Trees" out there - from elaborate to simple, you can probably find one that works for you. I love the idea of taking time to appreciate the things you might sometimes take for granted and it's an important quality to pass on, too.
This is probably the simplest thankful tree you'll come across. This was our last year's version. I drew a tree(-ish) outline on a large piece of paper, with many branches. No, it won't be winning any artistic awards, but it's not really about the tree, anyway, of course.
I used construction paper to cut out leaf shapes and then explained to Kay what the idea behind the whole project was. We tried to add one a day, and got the whole family in on it. She liked to write out her own leaves, which to me look like scribble but as long as it means something to her, I'm good with it.
Well after Christmas, when I tried taking the tree down, Kay got all upset. So it's been up for nearly a year now, reminding us every time we walk by that we have a whole tree-ful of things to be thankful for.
This is one thing I hope become an annual tradition in the Craig house!