There aren't many.
I want no flamewars on this site. Debate and discussion are fine, name-calling and abuse are not. I ask that you be respectful in your comments, not only of me but of the other posters.
No spam, obviously.
I also ask that commenters STAY ON TOPIC. I do close and lock the comments thread on most of my posts as they get old and discussion dies down, but I usually have three or four posts open at any one time. Please place your comments under the appropriate subject, instead of just adding them to whatever is the most recent post. Football threads are for the discussion of football, not writing. Writing threads are for discussion of writing, not football. If I post about OLD MARS, I welcome discussion of the anthology, anthologies in general, the participating writers, other books about Mars, even SF in general... but not about the GAME OF THRONES tv show, or the Jets, or how the novel is coming. Political discussion should be restricted to political posts.
If you want to write me a fan letter, send it via email. My address can be found on my website. Don't post it here. (And, sadly, don't expect a reply. I am about three thousand emails behind at the moment).