Of course, there are many, but to keep this short? I'll list only a few:
- POV - don't switch the point of view within a paragraph or even a scene if you can avoid it. Head hopping is what some call it. Not good. Very confusing to the reader. So, unless your character is schizophrenic, don't do it.
- Avoid flooding your writing with ellipses (...) or dashes (--) Don't judge. I used to do this. See me frowning? Yep.
- Avoid lengthy paragraphs. I mean, extremely long paragraphs tax a reader's patience.
- Avoid the exclamation mark, or at least use it sparingly. Instead, try including words that imply the excitement of the dialogue.
- Dialogue tags -- less is more. The "he said" or "she said" tags, sometimes called invisible tags, are really better to use. This doesn't mean you can't include descriptors throughout a conversation to let readers know what the characters are doing. In fact, you should include them.
- Cliches -- these aren't original, won't show your unique style, are totally boring and imply you are a lazy writer. I'm guilty of doing this. Still do when I'm writing the first draft. I get rid of most in later edits. They are nasty little things creeping into your mind, so watch out!
- Lack of specific knowledge and jargon -- If you plan on writing a novel set in China, you better know about the people, the geography, the culture, etc. Readers hate when they catch an author making errors this way. They cry foul and trash talk your book. Well, maybe not trash talk, but I doubt they buy anything else you write. Enough said.
- Use a clear font like Times Roman. No flowery, fancy type to distract the eye.
All righty then. I'm out of here. Don't let moss grow under your feet (cliche); write ... (ellipse), edit, improve. Follow the rules, but stay creative! (exclamation mark, though I think this one fits).