I know what you're thinking: the words Mechanics of Writing summon images of sitting in your High School English classroom diagramming sentences and trying to remember the definitions of adjectives, adverbs, and prepositional phrases. Although that's part of what I'm talking about, what we call the parts of a sentence isn't important; being able to write a sentence that expresses your thoughts is the goal.
All the fundamentals of writing begin at the sentence level. You can't write books unless you can write decent sentences. Notice, we're not talking about brilliant sentences, or even engaging sentences. Just sentences that do the work and convey your ideas.
For some of us, myself included, sentence structure comes fairly naturally, but when I entered the professional realm, I realized I needed to know a bit more. I began by rereading Strunk and White's Elements of Style. Notice I said rereading. If you haven't read it at least once, begin by doing so, and then read it again. (It's a thin book.) The section entitled An Approach to Style may or may not be useful, since everyone's writing style is different, but you should read it at least once. Strunk and White will remove a few of the more obvious mistakes from your writing.
Next, look at: The Art of Styling Sentences--20 Patterns for Success by Waddell, Esch, and Walker. This is a workbook. It is boring. But remember our goal—to become a writer as quickly as possible. Don't skip—go through every exercise until you have a firm command of the possibilities of sentence structure. Force yourself to do a pattern per day and you'll have it done in less than a month. When you are done, you should be able to write with variety and clarity. You want your novels to be clear and understandable, with continuity of thought within sentences and between paragraphs. This will help you achieve that goal.
Now that you finished the workbook and (hopefully) are beginning to understand sentence structure, I want to add something about ordering your sentences into a logical sequence of events. This may seem obvious, but it can be a problem. When you're writing, the only visuals your readers have are those they create in their minds as they read your words. If you have your characters do things out of sequence, your reader will be confused.
A simple example: John cringed. Bob pointed the gun directly at his heart.
Right away you probably see that the order is wrong and the two sentence should be reversed. (Assuming John doesn't have some other reason for cringing.) We could rewrite it as: "Bob pointed the gun directly at John's heart. John cringed." Now events are happening in the proper order. Every sentence you write needs to be in the correct sequence. And every paragraph should follow the previous paragraph in order. Same for chapters.
Please note that I'm not making any sort of rule about the use of Flashbacks or other techniques where the writer intentionally places information in non-linear sequence for story purposes. All I'm saying is that you want to give your reader your story in a logical pattern. After you've written a paragraph, check to see if it fits into the proper sequence. Make certain the writing is clear and shows the action you want it to show. Imagine yourself going through the motions of the character to see if they make sense.
Although editing is the final thing a writer should do on a manuscript, a book entitled Self Editing for Fiction Writers by Renni Browne and Dave King should be another of the first books you read. Like Strunk and White, it will show you some of the pitfalls of writing. It is important to understand that you shouldn't expect an editor to edit your sentences. The days are long gone when an editor will be willing to spend the time to "fix" your story. Editors are just too busy. Your manuscript must be as tight and well-written as you can make it before it ever reaches an agent or editor's desk. Publishing houses do employ copy editors who will proofread your work once your book has been accepted. Even in books that a writer painstakingly edits, a good copy editor will find mistakes. Their job is not to rewrite your sentences, however.
You should also obtain a book on manuscript format. Writer's Digest usually has one on the subject, or search the web for the information. Don't use forums to educate yourself on this, however. I see far too much misinformation out there. If you want to be a professional, you must present yourself as a professional. Your manuscript is the 'coat and tie' of your work. If your manuscript looks bad, you may be judged a novice before the editor or agent reads a single word. You are an unknown writer trying to make a positive impression in a world that knows nothing about you.
An example of manuscript format: when I began writing, the norm was that you put two spaces after a period. That made it easier for the printers to catch the end of the sentence. Oddly enough, this convention still seems to hold—I asked an editor not too long ago about it—I figured since everything was digital, I was actually causing the printer more work, because someone has to do a search and replace to delete one of those spaces in the finished manuscript. He told me he preferred I keep doing it the old way. Habits die hard.
Once you learn the proper manuscript format, use it regularly. It helps keep it in mind, and it's much easier, after finishing a first draft of a novel, if you have already put it in proper format from the beginning. NEVER send an editor a manuscript in anything less than proper format.
At this point you may be thinking: "I write pretty good sentences. I'll skip reading any of the books." Don't do it. Spend the time for the reward of publication. You may even find that your enjoy reading about the writing process.