A Conversation for Tick if You do Not Wish to Receive Further Information
Two other tricks...
First, in conjunction with the small writing, phrase it so it asks you to tick if you *do* want more information, but looks on the face of it as if it's the opposite.
Second, have the "Submit" button for the form, followed by a lengthy disclaimer, followed by a "Check if you want to opt out" box, on the assumption that most people won't scroll all the way down.
Key: Complain about this post