Here we go, example #1. (warning, it is a romance novel)
Fearful, the mere brush of his body, the scent of her emerging desires would infuse the air around them, she inched away from him.
What we have here is a case of the writer using commas to invoke emotion. It's an artistic way to break up the sentence, slow down the speed readers, and put them in the emotional state of the character. Basically, she's using the rule put a comma whenever you want the reader to take a breath.
However. There are three commas in this sentence, breaking it into 4 distinct parts. That's a lot of breaths. I wouldn't take that many breaths if I were sprinting. So it sounds odd and makes the reader go huh? Not good. Here is a possible fix:
Fearful that the mere brush of his body would cause a reaction in her, and the scent of her emerging desires would infuse the air around them, she inched away.
But, he went no further.
As far as I can tell, the writer was trying to use 'but' as a declarative sentence. But! He went no further. Despite popular belief about starting a sentence with a conjunction, writers do it if they want a particular sentence to ring out and stay with the reader.
Although what rang out to me was this comma. Yes, some sentences start with a comma after a single word (like this one). The rules on introductory clauses are a bit hazy. If sentences start with adverbs (slowly, basically, quietly), prepositional phrases (after the turn, under the bed), or when the introductionary word aims to modify the entire sentence. On the other hand, she started to get an understanding of commas.
But, he went no further is a comma after a conjunction. Not an adverb, preposition, nor modifier. I can't give you any explanation on what that comma is doing there. The reader doesn't need a breath; it's a short sentence. While the comma isn't breaking any rules per se, it isn't following any either. It's calling attention to the conjunction defiantly. Look! I started this sentence with a conjunction! That's right, I went there! Take that Strunk and White.
My conclusion here would be that if you are using your artistic license to start a sentence with a conjunction, DON'T put a comma after it. The sentence already stands out enough.
Without breaking eye contact with her he said to her sister, “Isabel, head back to...'
We have two out of three commas correct. Yes, you can put the speech tag before the dialogue. That comma after 'sister' is correct. So is the comma after Isabel. When using a person's name in a sentence, it's always separated by commas. Doesn't matter if it's at the beginning, middle, or end. A name is always treated as a paranthetical element.
The comma that is missing is after the introductionary clause. Without breaking eye contact with her,. I know I said it's okay to ditch the comma after an introduction. But this intro is so long, and the sentence has two distinct actions. Breaking (verb 1) and said (verb 2). This isn't a sentence like After the yardwork we'll get some ice cream where you can say easily in one breath and has only one verb. It breaks itself up into an action part 1 and action part 2. That's why it needs a comma.
"How un-wolf-like, of you, careful your human side is showing."
This is just an example of poor proofreading and editing. The only lesson to impart here is be VERY careful of what you allow others to see. It could end up on someone's blog. Proofread everything. Emails, memos, notes, blogs, tweets, facebook status, etc. I know people who have lost jobs and promotion opportunities because their emails and reports were full of errors. I don't care what you do for a living. Writer, plumber, architect, or teacher. There are people out there, like me, who are grammar snobs. Even if you are writing your mother, every piece of correspondence must be correct. You never know whose hands it will fall in.
"How unwolf-like of you. Careful, your human side is showing." rules for hyphens