I recently watched "After life" by Ricky Gervias on Netflix and this very question was answered.

"So if theres no god, whats to stop you murdering, raping and stealing as much as you want?"
"I do"
"What do you mean?"
"I do. I murder, rape and steal as much as I want to"
"But you dont"
"Yes I do"
"You don't murder and rape people"
"Thats because I don't want to. Not because some book tells me not to and I was the type of person that wanted to murder and rape? I doubt if some book would stop me anyway"

Base it on pragmatism. Don't do anything to someone else you would not like done to you.

How about trying to do the least harm & most good to those around you?....I have no idea about "evolution in this context......

Do unto others before they do unto you.

Definitely not. Evolution is not a good guide for morals. Try starting with the Golden Rule — “do as you would be done to by others” — and go from there.

It's what you should have always based your morals on kindness and empathy do unto others as you would have them do unto you

i don't understand what evolution has to do with morality. evolution is not a moral code. have you picked up a science book in your life? meanwhile, do you NOT know what is wrong or right? are you wondering whether to start robbing banks and raping infants? i think most folks know the difference between wrong and right without relying on a big ol' book with a gazillion conflicting translations. you can decide for yourself whether to eat fish on friday but i think you know not to trip the little old lady trying to cross the street.

g

p.s. did you ever figure out that lying is kind of a bad thing? how the hell can you be an atheist, an agnostic, a secularist and religious all at once? i gave you the benefit of an honest answer before looking at your profile because, well, i DO that. now all i am doing is thinking what a creep you must be.

"how do I decide what is right morally" - Have you ever tried common sense?

Morals are how you treat others a religion does not give you therm you have them or you don't

You really need to figure these things out for yourself.

Morality is common sense. We kno what is right and wrong. Don't need in imaginary man in the sky to tell us.

I've been an atheist for decades, and I strive to live my life in accordance with the Golden Rule, as espoused by Confucius - if you don't want it done to you, don't do it to others.

Golden rule.. do unto others... treat people how you want to be treated.

Why 'base' it on anything? Make your own choices and accept your own consequences and credit.

Years ago my wife pointed out to me how close the classic Greek Stoics were to my personal philosophy. How's that for saying make your own answer... then answering.