What is the difference between the table of contents of a book and its index? what information is contained in a reader's guide entry? why would you use who's who? what would you go to a reference librarian for?

Answer to Q.#1: The Table of Contents is where you can find page numbers for specific TOPICS but the Index shows specific WORDS in a book.
Answer to Q.#2: The information is a Reader's Guide Entry is stuff that you either need to know or should want to know.
Answer to Q.#3: You should use this phrase when your trying to figure out whose this person and that person.
Answer to Q.#4: You should go to a Reference Librarian when, (a) Your looking for best book on the topic currently on/ in your mind, (b) If your not sue where to find the book your looking for or (c) your just clueless on which book you need for an assignment/ project. 

Bis the best answer.