When stating a book title, is the comma before or after the quotations?
The best possible answer is: whatever your teacher thinks is correct. I'm not kidding. Sometimes teachers just get it wrong, and it's often best to just keep your mouth shut and go along with what the teacher thinks. The normal rules about quotation marks are also slightly different in Britain and America.
With that out of the way, here's the answer. If you follow the rules of British English, put the comma outside the quotes:
In the book "Charlotte's Web", Charlotte is a spider who wants to....
because that matches the structure of the sentence. If you follow the rules of American English, put the comma inside the quotes:
In the book "Charlotte's Web," Charlotte is a spider who wants to....
because that looks prettier.
In British English, the rule about putting a comma inside the quotes is only for when you are quoting what somebody said:
"Look at Charlotte's web," said Wilbur.
If you are using a word processor, it's probably better to use an italic font to mark the title, like this:
In the book Charlotte's Web, Charlotte is a spider who wants to....
but, again, this depends on your teacher's attitude.