Another use for commas is when you are addressing someone in a sentence.
"Hey Bob, come over here," he said.
That is how I see most sentences. It should be;
"Hey, Bob, come over here," he said.
Another example - "I just called, Mom, to let you know where I am," Sam heard Joe saying on the telephone.
And when the person is addressing someone directly, like above, (mom, dad, brother, sister) then it should start with a capital.
I have a hard time with first, second, third person. So I don't know what person this is in, but this is when you don't capitalize;
"I just talked to my mom," He said.
Or
"Thanks, Sam, for letting me call my mom," Joe said.
When I went through school, I was taught that all words in the begining of a double quote, (") was capitalized.
He said, "Come here."
I was also taught that all words after the quote (") was to be capitalized as well.
"Come here," He said.
The exeption to the rule would be;
"Come here," said Sam.
Boy on a String