Inventing alien cultures is one of the hardest things any writer of speculative fiction can attempt. Too many purportedly alien cultures are nothing more than human cultures in disguise. Star Trek's Klingons are only the West's perception of medieval Japanese warrior culture pretending to be that of humanoid creatures from another planet.
Cultures are created out of mixture of values and behaviour modified by a series of historical accidents and refracted by social, political, environmental and economic circumstances. This means even human cultures can be alien relative to other human cultures.
To put it crassly, Zulus, Cambodians and Finlanders don't basically share American cultural values and are only waiting for them to break out and be expressed in the world. However, humans everywhere want to be treated fairly, shown respect, and want their points of views and opinions to be considered in decisions affecting them.
Sticking with humans, we generally share common emotional responses to what hurts us and what makes us feel good. Consider the following hypothetical example. A woman is jilted and left at the church unwed. In front of all her friends and family, she is devastated. This is her human reaction to this set of circumstances. Different cultures determine different responses.
Culture A: She is ruined woman and commits suicide.
Culture B: Her brothers swear vengeance to hunt down the bounder and surgically remove parts of his anatomy.
Culture C: She says rats! There are plenty of fish in the sea. Everybody goes to the Wedding Party that isn't a Wedding Party and gets merry.
These are hypothetical cultural responses. Their emotional basis remains a human response. Behaviour and the values determining what they do in response are what constitutes their culture.
Now a truly *alien alien will be a creature with a different culture shaped by different history, different economic circumstances, different political political systems, different legal systems, a different environment on their home planet, and what can make even more dificult a different biology.
So much of human culture is driven by our basic biology and especially our reproductive behaviour and biology. Aliens from advanced technological civilizations will have found out how to control their biologies and modify their behaviour to their own advantage.
Creating aliens with different evolutionary histories and different biologies is hard enough, without trying to create cultures appropriate to them.
So fat this answer has discussed the simple fact that creating aliens is hard, and creating alien cultures is even harder. However, it is reasonable to assume that ethical behaviour will be common to any sapient species anywhere in the universe. Humans and aliens will probably share similar ideas about fairness, kindness and good behaviour. Their values may radically modify how and what is considered fair, kind, just, and behaving well. But it will be the common ground between your bratty Sarah and her Moon-based alien friend.
Apologies for taking the long way around to get to the point.