Selecting a genre for your new book can be a difficult process, especially for a new writer. Remembering a few things will make your selection easier. Every genre is made up of several sub-genres and finding the right fit will help you write a story that will be published.
Write what you know. If you are not writing in a genre you are comfortable with, it will show. Editors expect writers to be able to handle the genre they choose and make the content believable. If you are beyond your depth, this is impossible.
Research your genre. Many writers fail to properly investigate a genre. Read numerous books from different authors in your genre. While you do not want to imitate them, it will give you a better idea of sub-genres as well as how these writers handled the genre.
Research what is selling. The sad truth is, not all genres are popular, and breaking into a particularly difficult genre can be nearly impossible. Look at what publishers are interested in and which books are doing well on the bestseller lists. Just because you feel drawn to an obscure genre does not mean that it will sell. Some genres are so limited that only a handful of publishers work on them, and breaking in can be an exercise in futility.
Picking a genre doesn't have to be painful. Listen to your story, make sure you are capable of writing in the genre, and it is a marketable one. If you have these things in place you will be more likely to find success.