"남자가 왼쪽에 있고 여자아이가 오른쪽에 있어요."
Translation:The man is on the left and the girl is on the right.
I don't have a mnemonic per se, but it's always helped me to remember the etymology of the words, and the fact that people have been biased against left-handedness forever: 오른 is from 옳다, meaning "to be right, true, proper" (good); 왼 from 외다, meaning "to be wrongly oriented" (bad) -- think 외국인, 'foreigner', those people from the "bad/left" side of the world.
That's true, (like 시외 버스 is the intercity bus because it travels 'outside' the city) but I was trying to draw a semantic connection between the words. While 왼 is of native Korean origin and 외 (外) is Sino-Korean, I believe they influenced each other at some point for symbolic resonance, since foreigners are historically 'outside' of what is normal in Korea like being left-handed and associated with a left-hand path is 'outside' of what is normal all over the world.
In Korean it's the other way around though :D 오른쪽 comes from 옳다, which roughly means sth like to be right and therefore right is lit. "the right direction(쪽)" and the odd one is left, 왼쪽, which I'm not sure but may have a relation to the Korean word 외 for "out". So more like it is outside of what is normal, they are most likely called this way because left-handed people are usually a minority and people therefore assume the right to be the normal way for mostly everything
Reference: sean.mullen's comment above
It comes from the fact that your left side of the brain knows names for things. In experiments of people with a split brain, they can't name objects if only the right side sees them.
But the left side of the brain controls the right side of the body, so it has a bias towards which side is better
the conjunction article, "고" that is attached to the first verb in the sentence, "있고" is the conjunctive verb phrase that hinges the sentence together, properly translated as "and". It is a contraction of "있어요 허고" but saying it that way does not flow fluently, thus, the contraction.