From many writing theories, you might find that the things you should do when writing fiction novels is determining plot, characterization, etc. Actually, the only thing you should do before plotting and characterizing, you should decide what genre your novel will be. Is it a romance, historical, science fiction, or suspense?
The first thing to consider is what type of books you normally read and in what genre people love most. A lot of people may tell what kind of genre which can produce lots of bucks for example if sales of vampire books are increasing, write a vampire book. It actually is not a good idea though it may sound logical.
You can simply think of what section of the book store you normally head for when you go shopping for something new to read. Don’t consider writing romantic fiction if you avoid the romance section. In general, you’ll have the easiest time writing if you stick with the areas you are interested in.
There are many sub-genres to explore within any genre after all. If you are a reader of romance fiction you can write historical romance, time travel, fantasy or even vampire. By the same token, mystery readers can delve into thriller/mystery, science fiction, and/or horror. You must simply decide what you love to read and then write a similar book.