There are a number of common themes in writing, which is why almost all the bestsellers have certain recurring elements. Of course, there's also a number of hopelessly overplayed and worn out tricks better left for the hacks. Learn to tell the two apart and your odds of getting a shot at the big time will go up dramatically.
A List of Common Themes in Writing
This is by no means a complete list; there are plenty more themes out there. These are, however, some of the most frequent ones you'll find in successful books.
Almost every single book on the bestseller lists has a love subplot. Sometimes it's even the main plot, although these books usually don't make the New York Times list. Why would a list of authors as diverse as Dean Koontz, Douglas Adams, Jane Austin and others come together and cram love into horror, sci-fi, comedy and practically every other conceivable type of story?
The answer is simple; people love to see relationships form. And it allows for the author to develop the characters in a new dimension. This is particularly important for thrillers and action heavy stories where the lead can easily turn into a stereotypical Rambo-clone without a counterpart with whom to reaffirm a human side between fights and scares.
Used sparingly, an author can make a sudden, dramatic loss of a beloved character one of the main turning points of a 500-page book. It triggers righteous anger and determination that spurs the remaining hero into action, or it can be the sobering event that rocks a key character from the edge of insanity.
The test of friendship, usually in the face of temptation or severe adversity, is another classic element in writing. Will the loose acquaintance step up at the moment of truth, and will the best friend turn out to be of the fair-weather variety? Either way, it lays the groundwork for a more philosophical aspect of the story.
Good vs. Evil
Like love, almost every good story has a struggle between good and evil, with evil usually having the upper hand. It can be an evil medieval conqueror, a superior alien race or a giant, faceless corporation. In any case, the good side, by virtue of being just and righteous, has a core strength that evil lacks. On the other hand, evil is fraying from the inside due to mistrust, greed and corruption, which tends to create fissures and breakdowns at key junctures just as the good side gets a boost.
No good horror movie director puts the title monster in a close-up the first minute. By the same token, no writer should put every card on the table in chapter one. While not all stories lend themselves to the kind of drawn out process of a murder mystery novel, it is usually wise to save a surprise or two for the latter half of the book.
Look at the phenomenal success of the Harry Potter series. While the crisp writing and the evergreen fascination with magic certainly were part of its success, it is also worth noting that the whole "suddenly yanked away from the dull everyday life" aspect played in too.
What kid, orphaned or otherwise, doesn't fantasize about suddenly getting invited to a wizard school? Or Narnia; there's no income requirement, race or religious restriction, school grade entry criteria, or any other limitation we face in reality -- just step into the closet and you're in a fairy tale. The more easily accessible, the more "it could happen to me" you can make it, the more the reader tends to be taken into the story.
Coming of Age
Like love and friendship, the coming of age is another classic ingredient that allows the main characters to develop depth while keeping the focus on the bigger events. War stories where the characters are transformed from careless and perhaps naive farm boys to humbled yet jaded young men are a staple. However, there are still plenty of other scenarios that lend themselves well to a good coming of age theme.
Again, these were just some of the most common themes in writing you'll encounter. Read a lot of different books that have done well, current as well as historical, and you'll recognize these and many other themes and tricks. It's no coincidence the successful books share so many of them. The question is how YOU can weave them into your next project. Good luck!