Jesus forgives the repentant criminal

Then he said, "Jesus, remember me when you come into your kingdom.[1] " 
Jesus answered him, "I tell you the truth, today you will be with me in paradise." 

Luke 23:42-43

Take some time to write a note to God. It can take whatever form you like about whatever you like - even just a name, a time, a place. God knows.

Leave it on the cross. These will be burned and the ashes scattered to the wind.