‘Baker stormed out the room. When he had left, Atkins sank back in his chair.’
What the writer meant was, when Baker had left, but the sentence implies that Atkins had left. This is a common error, committed even by established writers. When re-reading for the final self-edit, check the sense of your sentences.
‘Go away!’ he hissed. This is a pet hate because to hiss is to make a sibilant sound, like that of a snake, which means there have to be some esses in the spoken words. Again, careless published authors commit this error.
Lengthy speech is very annoying. Few people in real life talk non-stop for what amounts to half a page or more. This is lazy writing, dumping information without thought. Fine, some established writers might get away with it, but it is to be abhorred. If characters are speaking, natural conversation involves interruptions, gestures, asides – all breaking up the otherwise lengthy speech. Try to remember that any paragraph of unbroken dialogue over three lines in length is suspect.
A flat storyline with little in the way of conflict is going to end up being rejected. Without conflict, there is no plot and no pressure for the main character, and essentially no story.
Exposition for the reader’s benefit is not only unwelcome, it turns off most editors. No two characters should ever mention in dialogue anything that both of them know already.
Using the wrong words can be forgiven, perhaps, but I’d advocate that writers should try to avoid the usual pitfalls. One bestselling writer uses ‘adverse’ when he means ‘averse,’ for example. I could cite several.
Word repetition (what can be termed word echo) shows up lazy or inadequate self-editing and may be excused unless it becomes frequent and thus annoying, in which case it may point to the rejection bin.