Over on the F&SF forum he says:
Here's the deal:
1) Go to our "Contact Us" page: http://www.sfsite.com/fsf/contact.htm
2) Say you'll blog about the issue and tell us where to mail your copy of the issue.
3) Receive the issue and blog about it. Naturally, we prefer if you read the issue before blogging about it, but I'm just insisting that you blog about it. (The first time we tried this promotion, people mistakenly thought they should blog about the magazine before receiving the issue. No. Get the issue first, then blog about it. Say anything you like about the issue.)
4) Send us a link to your blog.
That's all there is to it, except to say that if you were in on the blogging promotion for our July or August issue, please sit this one out.
Looks like a great issue: Stephen King, M. Rickert, Albert Cowdrey, Carol Emshwiller, Terry Bisson, Stephen Utley, Michael Swanwick... hurry before they're all gone.