Thor's Thoughts: World Building Cultures
Good day, fair writers. And may I take a moment to wish you a pleasant holiday? I know not who this Saint Patrick is, nor what his affinity for green is meant to represent. Humans have odd holidays.
Which brings me to part of my point today. In writing, especially speculative fiction, it is important that we pay attention in world building. If your story takes place in the human world, you have experience to draw from. However, if your story takes place in a different land (for example, Asgard) you would require an entirely different set of colloquialisms, holidays, flora and fauna, and quite possibly currency.
Many authors create a world that is quite similar to Earth in most respects. This is for a purpose. It serves to provide familiarity to the human reader and, therefore, a sense of security. In other words, it helps with the learning curve of the world. Along with the basic similarities, however, it is wise to provide some drastic difference which will set your world apart. You do not want to use a world or have anything too similar to anything that has been used before.
In the Fantasy genre, it has been a practice for many years to base worlds off of existing European cultures -- particularly Great Britain. In recent years, that mold has begun to shift with the help of such authors as Saladin Ahmed, Brandon Sanderson, Guy Gavriel Kay, and others. (Listen to Saladin, Brandon and others talk about this here.)
In Science Fiction, there are different ways to push and pull. If you are building an alien world you have a huge amount of freedom. If you are writing a future-earth based on existing human civilization, you are somewhat more limited in scope in that there is a history already built, from which you must draw. If you do not, your readers will expect a different history and assume your world is not human-based.
In most cases, it is always better to go too far and possibly have to pull back, than to not go far enough. Use your best judgement, but remember: Hobbits did not exist before Tolkien. Quidditch did not exist before Rowling. And your world cannot come from anyone else's mind but your own.
Build carefully, and use your imagination. Good luck.