The biggest issue I see in world building and storytelling is the portrayal aliens as carbon copies of humans, who do everything that humans do but whose only difference is a slight forehead bulge. I guess it’s safe in some ways, and for well-written stories, human-like aliens can serve as a doorway into an alien culture or reflection of humanity.
That said, there are far too many poor examples of aliens who look at humans with only disdain, anger or disgust. While it may help the story a little, the trope is used far too often to have the punch it did in the 60’s.
Audiences are used to the angry alien trope, so work created with aliens having more of a facted nature to them are much more attractive than the monocultured aliens of yore.
So when writing for aliens, when you don’t need a humanoid creature to reflect or observe humanity (still a legitimate trope), a truly unique alien might do the trick.
Ugly Bags of Mostly Water
Some of the best sci fi will observe humans from a very odd perspective. The aliens themselves may not be bicameral (two eyes, two ears, etc) but tri or quadricameral. They may be bicameral with tricameral traits, etc.
To view humans
There are many things we do as humans that can be taken for granted in science fiction, and are often overlooked.
Humans see a part of the electromagnetic spectrum that we deem ‘visible.’ However, another species may deem their ‘visible’ light in the region of the EM spectrum we call “Infrared” or “Ultraviolet.” Some beings may even only reflect that light and bend all other light, making them invisible to us. That said, we may be invisible to them if we wear infrared-absorbing suits.
Some creatures hear in greater range than humans. This means that sounds that are normal levels to us may be deafening for aliens. Some may not even hear at all, but communicate via vibrations.
Speech is also something completely overlooked. Whale Song, Bird Chirps, Dolphin Calls and other forms of communication work vocally. However, in many ways (such as with Dolphins), the calls can be produced without vocal chords. This is why we have yet to communicate with dolphins, because there is no real cypher. However, recently scientists have noticed that a sound burst from a dolphin reads as a pictogram, which may be the Rosetta stone of communication. The pictures produced by the sounds are call cymaglyphs.
That said, if aliens used a similar device, our way of speaking would be indecipherable.
For human speech, the aliens may not be able to distinguish speech from song, because speech is song.
While bad sci fi usually depicts all aliens as stronger than humans, the probability of low gravity creatures would make them significantly less strong than humans, while those of higher gravity may be stronger. See Sir Arthur Conan Doyle’s books on those effects.
If creatures exist that have sufficient intelligence to build a starship, it does not mean they will think in basic numerical terms like western humans. Humans have been proven to think logarithmically, so it doesn’t make any sense that other creatures would follow the same patterns of westernized American thinking that humans are mostly portrayed to do.
For instance, the Sumerian number system, and the scientific article on logarithmic thinking are different than our current method of teaching children basic mathematical concepts.