A Brief Conversation:
As both a writer and an editor, I have found that the most common reason for stories being rejected is due to improper formatting of conversations. If you follow the rules set out here, I can't guarantee that your story will be accepted, but it won't be rejected for conversation errors. I strongly recommend the essay
How To Make Characters Talk.
This post doesn't replace that one, but is intended to cover the basics in one page. I am writing it as a conversation to demonstrate the rules in action.
"What is a conversation?" you ask.
I answer, "This is."
This exchange consists of quotes by two different speakers. The words spoken are set off by quotation marks (aka 'double quotes'). The punctuation for what they say goes inside the quotation marks. Each time the speaker changes, the change is marked by starting a new paragraph. These few rules will fix most of the issues involving formatting conversation. Honest!
You persist. "There has to be more to it."
"There's a lot more, but a vast majority of the problems are addressed by following just two rules. Punctuation goes inside the quote and a new paragraph is needed every time the speaker changes." You clearly aren't convinced, so I continue. "
Strunk and White
has a chapter devoted to the issue, but most of the errors that lead to stories being rejected involve just these two rules.
"Of course there are other rules. For example, if the quote spans more than one paragraph, there is no closing quote at the end of the first paragraph, but the following paragraph opens with a quotation mark. This helps readers keep track of who's talking. I didn't make the rules, but I pretty much have them down."