concrete "footer" (12" diameter, depth to 6" below frost line). I embedded an L bolt in that at the time of pour, then bolted on a galvanized post bracket. The 4x4 was then screwed into the bracket. Both decks over 20 years in place, no failure.

Thanks to Nichter....

I see that I misread the request - you are right, fence post application is entirely different. For fencing, I've used a gravel base at the bottom of the hole, and dry-packed concrete to fill in the hole around the post.