The Dreaded Reformat

My computer is getting to the stage where I think the best thing to do is to reformat it. It’s always been something I’ve dreaded having to do. Will I remember to backup everything I want to keep? You just know there will be something you missed, like your internet bookmarks or some application preferences stored in some obscure file in some obscure folder on your HD.

What should be on your to-do list before reformatting your computer? Is there any specific ritual you go through? Please enlighten me!