We've heard the words, Write What You Know, but do we understand what they mean? The words can be misleading and may discourage new writers from branching out to try new genres. Do they mean we should only write about our experiences? No. They mean we should write what we know; and we know more than we think we do.
What needs knowing is what it's like to be a human being. Everything else--occupations, places, times-everything--can be researched.
Know Your Characters
People are people. It doesn't matter which time line they're in or the world you put them on, they are still people. Look at the people you know and use their odd habits and characteristics, along with your imagination to make your characters come alive for your readers.
Know Your History
Researching will teach you all about the physical aspects of your chosen time period. You can learn the modes of dress, speech and the type of government of any time period on earth.
Whether aliens in another galaxy where only your imagination sets the rules, or Earth two thousand years ago, you have to give them traits that humans, your readers, can identify with, or the story won't work. Can you see your stoic, stern grandfather as ruler of a distant planet? What about the zany aunt who loves to wear loads of costume jewelry? A perfect Queen.
Everyone has experienced love, fear, hate, curiosity, just as you do. Take what you know and turn on your imagination, then mix it with the knowledge you've gained from your research. Your characters may be vampires, evil gods or aliens, but they will feel the same pain and fear that you do. They will feel love and compassion.
You know what frightens you. You know the feeling of being afraid. This is what makes the stories believable to others: your fear of dark places, of the unknown, pain and death--primal emotions that everyone shares. If it frightens you, it will probably frighten others. The same with love, happiness, sadness, anger--emotions are universal to all people. You know what causes these feelings in you, and know what happens to your body while under the influence of these feelings.
If a character falls into a icy creek and you're unable to describe the feeling well enough for the reader to feel it; go jump into an icy creek. This is extreme of course, and I donít advise it, but you'd only have to do it once to remember the feeling through hundreds of stories. You can use this feeling in many ways, being lost on a frozen mountain, for instance.
Everyone, whether they admit it or not, has felt so angry, if only for a split second, that they could commit murder. Remember that feeling and use it. Fiction is truth - exaggerated.
Readers will identify with the characters, thus the story, because they have felt the same.
Write what you know is good advice, and you know more than you thought you did.