clipped from: artjunk.typepad.com 
I start with putting wax paper down under each page to prevent sticking, mess, etc...
Then I use gesso to prepare the page. Gesso is like white paint primer. You can find in painting isle. It helps give page some body and prevents paint from soaking in. Please note though that you will not have "perfect" results in a composition book. There will still be some wrinkling, buckling, but I assure you they are fun to work in and great as a art journal!
I'm really into working on my art journal again. I am using composition books as I did for my first one. I found this old tutorial I did for my niece last summer. I am posting here for anyone interested in starting there own. You can see more journal junk examples in my flickr album. Here you go!