A Little Heaven/Hell Headcanon
Since neither the book nor the show for Good Omens really address how it's decided who goes to Heaven vs. who goes to Hell, and what happens once a human soul gets to their "destination," I developed my own headcanon for this, that I use in my fanfic (vaguely in Born of Starlight, but definitely more direct definition is upcoming in Trust Fall). At the risk of getting totally destroyed by the fandom, I thought I'd share how I'm defining it (please keep in mind: THIS IS MY HEADCANON. No one said you have to agree. If you don't like it, just keep scrolling, and don't read my fanfic. It's that simple to not be a dick.)...
Headcanon regarding Heaven/Hell and final rewards/punishments
Heaven:
In Heaven, most people's spirits are processed through back to Earth again (reincarnated), if they are deemed to have lived a good life (as determined through Earth Observation Files). Only the very best souls, or those who make the greatest sacrifices, are offered a chance to stay, by becoming angels.
Hell:
People whose Sin Ledgers (something I created to balance out the Earth Observation Files and simultaneously explain the teetering stacks of paperwork, everywhere) are only full of vague offenses or who have shown themselves to be capable of either endless hours of drudgery or of convincing other people to do evil things, are given the opportunity to become members of "the Damned" -- a rank just below actual demons. Those who have been marked as "Punishment Required" or deemed too dangerous to Hell's authority are processed through into Eternal Torment.