There are a handful of very simple things you can do to improve your writing. I’ll venture to say that all novice writers who have not been trained as writers make these mistakes. I suggest you experiment. Save a working copy of your manuscript, then go through and make the changes I suggest here. See if it isn’t better. You may have difficulty at first, because you write the way you talk. But don’t do it. Yeah, in dialogue you sometimes have a tag for a character, such as he says “you” instead of “your,” but look at what other authors have done. Analyze their writing.
1. Go on a Which hunt. A good rule I learned in law school was to go on a “which” hunt. Go through and replace “which” with “that.” Then take out all the “that’s.” Many people use “which” when it should be “that,” and many people use “that” when there should be no “that.”
With the exception of statements such as, “That one,” or “Which one?” or “I don’t believe that,” and such, just go ahead and take out all the whiches and that’s. Then read it and see what you think.
2, Dialogue Tags. Only use “said” or “asked” as a dialogue tag. A sure sign of an amateur is over-using adjectives (“ly” words) as dialogue tags. “Come to my house,” he said, wryly. This is author intervention when the way in which he said it should be discernible from the context and from his gestures and expression. Instead: He looked at her from the corner of his eye. “Come to my house.”
Don’t use any tag other than to make sure the reader understands who’s speaking.
3. No Superfluous Words. Words such as really, just, a little, some, somewhat, almost, actually, a bit, well and so to start dialogue, are all extra. Take them out. Also consider carefully using appeared, seemed, and apparently. “It appeared to float.” It either floated or it didn’t. Did it look as though it floated, but it really had legs? Then say that. But if in your story the thing is floating, then say “it floated.”
4. No Semicolons. Beginning writers love to use semicolons. I have no idea why, but I see it time after time. Don’t use them. They are rarely necessary, and unless you have a degree in English, you probably don’t know how to use them, and you will look like a moron to an editor or agent. Leave them out. Just use a period.
5. Keep it Simple. Use a simple word or phrase instead of complicated ones. Why say “He strove to obtain,” when “He tried to get” works just as well? Use “before” instead of “prior to.” Your object as a writer is clarity, not to prove to the world that you can use big words. Tell the story, don’t obscure it. Take your Thesaurus and throw it into the abyss.