One of the first aspects that you should consider while planning your book is whether your setting will be real or fictional. It can be good fun to invent a setting but writing what you know also has its benefits. If you live near a unique little town, for instance, you may choose to capture it in your story. Walk down its streets, talk to neighbors, read up on its history, visit the local museum. You may find that in investigating a possible setting, a story presents itself to you. Little towns are perfect settings for romance novels and cozy mysteries.
Next, you will want to consider what role your setting is going to play. Will your setting be the antagonist? Many genres set man against nature—westerns, nature/adventure, war, and apocalyptic stories all have the protagonist fighting for survival against an unforgiving backdrop.
Use your setting to create the tone and mood in your story. Fitzgerald utilized this technique perfectly in The Great Gatsby. The story begins in the spring when life is full of promise, progresses to the climax on the hottest day of summer, and comes to an end as the leaves are falling from the trees. How will your setting convey the mood of your story? Detective stories, as an example, require suspense. Therefore, you will most likely want a decrepit squad room, dirty city streets, and dreary daylight. Consider the following: How will a lake surrounded by woodland appear different in a love story than in a murder mystery?
As you construct a setting, consider the five senses. Your readers will experience the setting through what your character sees, smells, hears, tastes, and touches. Your job as a writer is to make your readers believe in the world that you have created. Consider the lengths that Tolkien went to when creating Middle Earth in his Lord of the Rings trilogy, for instance.
A word of caution, however. You do not want to provide so many details that your setting description becomes dull to your readers. Nor do you want to skip a description of the setting all together as it is what provides a sense of time and place for your story. You should always be selective when deciding which details to include. Make them vivid; make them interesting; make them memorable. Happy writing!