How do people who use the Bible as a bases for their Christianity decide what is literal and what is not?
On the basis of whether they think can get away with it. Earth rests on pillars? Not literal. Thunder is God shouting? Not literal. Geocentrism ... tricky one, could go either way, depending on how little science you know and how conceited you are. A six-day creation? Well, as this forum shows, they've got that one covered. Not well, but they
think they've got it covered.
It's the same with the moral aspects, they go with what's socially acceptable in their neck of the woods. God says to stone homosexuals? OK, let's not actually stone homosexuals, but let's ban gay marriage as a sort of token gesture. God says to stone women who aren't virgins when they marry? Not even going to touch it. God permits slavery, but it's still wrong unless you're talking to white conservatives in the South. God
does forbid lending money at interest, but as this is practically the foundation of capitalism, and capitalism is God's way, as we know from ... from ... from somewhere ... we'll just pretend that that never happened.
Basically, it's always going to be easier to
impose your prejudices on the "Word of God" then to
get your prejudices from the "Word of God", because if you did the latter, society might disapprove of you, whereas if you play it safe and go with the former ... well, what's God going to do? Send bears to eat you, like in the Bible? Send a plague of locusts, like in the Bible? Smite you with boils, like in the Bible? Make you eat grass like an ox, like in the Bible? Nuh-uh. He's not even going to argue. We all know he doesn't do stuff like that. So you really have nothing to lose.
It's a funny old world, isn't it?