1.Ensure 100% that the ads can't serve me viruses, worms or any other nasties (and that they aren't trying to get people to install such software via the ad)
2.No ads that play audio
3.No ads that cover the content
4.No ads that contain elements pretending to be UI or otherwise attempting to mislead people into clicking on them. (including things that try to get people to install spyware, adware or other undesirable software)
5.No ads for anything that is illegal, of questionable legality or attempts to defraud or scam people (online gambling, porn, get-rich-quick schemes, questionable weight loss schemes that don't actually work etc)
and 6.Geolocate my IP address and serve me ads for things actually available to me here in Australia. No more ads for US-only things please. (that includes US charities, lobby groups, special interest groups, things like AARP etc)
Of course ad providers will do none of these things so I will continue to block their ads.