I go by equal exchange. Depending on how truely thankful you are. If it is simple, I will smile up at the sky and say thanks with all my heart. (cheesey as it sounds.)
If it involves healing for family or friends, I do a prayer of thanks.
When it is something that means a lot to me, I will do a ritual/celebration for thanks. Such as burning a fire, cadles, and more.
I even sometimes bury something of mine as a gift to the earth.
Just what ever feels right to you, the universe already knows your thankful or not. It is your choice to show them in your own way.