Character, setting, theme, POV, and conflict/plot are the main elements of fiction and pretty much summarize the fundamentals on which editors and agents concentrate. Weakness in any of these areas can suck the life out of areas that are stronger, but every writer has their strengths and weaknesses. Few are masters at all elements and writers can spend a lifetime achieving mastery of only one.
To give an example, let’s say the author spends loads of time setting the scene at the novel’s beginning and none in getting conflict started or the main character developed. I’m not saying here that an author has to concentrate on all these elements as some areas are more essential than others, depending on the genre in which the book is being written. For instance, if a novel is plot-driven, as most pure genre novels are, then less time is spent on character development (however, that's not to say the characters aren’t developed) and more on making sure the plot moves forward rapidly, thus creating the page turner on which genre depends so heavily. However, if one is developing a novel that plays more on the readers’ emotions, then character, setting, theme and point of view come first, whereas conflict/plot are left to develop more slowly (but not too slowly and it has to be there). The art of bringing the elements together, making sure each is nuanced just so to get the story across, is the craft of fiction. As a writer, you need to understand the elements of fiction, your goals, the genre you write in, your ability, etc.
People write for a variety of reasons, but those who write successfully usually fall into two categories: entertainers and commentators on the human experience. To develop a novel and use your elements wisely, you need to know why you are engaging in the writing process.
I mentioned ability above. This is something else that is important for every writer to comprehend: no matter what level you start at, your writing ability grows and changes over time, just like fiction itself does. Some people start at a very low level (more weaknesses than strengths) and others start at a very high level (more strengths than weaknesses), but all writers share a common trait. If they continue to write, some part of their skillset will improve or change, for better or worse. Even published authors deal with this. At this point, you are all probably thinking that you know of published authors who have had one great novel and then a clunker…or three…or four. Usually, this is a result of other factors working against the creative ability once the author is published. Also, as one skill plateaus so another can be worked on, the writer has to go back and get up to speed on the skill he hasn’t focused on for quite some time as he’s improving in other areas. This is why some books may feel a bit uneven.
If you’ve heard of the “sophomore blues” then you know what we are talking about. No matter the skill level, it never gets easier to write that next novel. It may feel easier, but that doesn’t mean it is.
There are miles and miles to travel on these subjects, but to make this post short possibly more likely to be read, we are going to stop here and continue later.