Although I am a big advocate of writers writing whatever they feel like writing (and in whatever form they choose), I think there are a few things writers should avoid.
POV Overload
With this I mean: don’t write your story from the point of view of everyone and his uncle. Especially not if that particular POV doesn’t add something vital to the story. I have read too many books with more than 5 POVs, most of which sounded so similar it was hard to tell who was ‘speaking’ at the time. If you are going to use more than 3 POVs, make sure all the POVs are really needed to tell your story the best way, and all characters bring something unique to the story.
Head Hopping
If you are writing the story from multiple points of view, make sure you don’t head hop. I have to say that this is my greatest pet peeve and I will stop reading a book written in third person limited with multiple points of view where the POV changes in the middle of a scene. If you want to change POVs, do it after a scene break, or better yet, change POVs when you change chapters. I know that an omniscient POV can describe things the main character doesn’t see or doesn’t know about, but a lot of writers go too intimate with the third person narrative for it to be omniscient.
Clever (or no) Dialogue Tags
‘He said’, ‘she said’ dialogue tags are your friend. A lot of writers try to be clever with their dialogue tags, substituting ‘said’ for a host of different words, but that just gets distracting. The average reader doesn’t consciously read ‘said’, but it is an easy way to indicate who is speaking. Sure, you don’t have to use dialogue tags at all, but if you choose that route, at least make sure the reader knows who is speaking. I usually find myself losing the thread of conversation halfway through if there are no dialogue tags (and when I go back and insert the ‘he said’ ‘she said’ tags myself I often find the writer has confused him/herself as well).
Info Dumping
So you have done a lot of research for your book. You now feel you are an expert on bull fighting, for example, because one of your main characters gets stuck at a bull fight. You would like to show off this newfound knowledge. Resist. Do not dump all that research on the page. Your reader doesn’t care how much you know. They don’t want to know all the ins and outs of bull fighting. They only want to know what is relelvant to the story (which is often very little). The purpose of research is to make a particular scene in your book more realistic, so fight the urge to show off. No one likes a show off.
Subplots are Not Main Plots
It can happen while writing your book that your subplot becomes more interesting than your main plot. If that is the case, rewrite your book so that the subplot becomes your main plot and your main plot the subplot. Do not plow on and allow the subplot to become the main plot halfway through the book as that will only confuse the readers. This seems fairly basic advice, but I have read books where this happened and it’s hella confusing, not to mention frustrating when the main plot is abandoned.
Mary Sue Characters
Don’t create Mary Sue characters and whatever the male equivalent of that is. I get the desire for creating perfect characters, but they are very boring to read about. Characters need flaws, whether or not they overcome these flaws. The opposite is true too: don’t create villains who don’t have a speck of human decency in them. The most compelling characters have a bit of both. And let’s face it: a good novel stands or falls by the characters.