Q:

For titles on questions, which of these is better: Author of the book- Chapter number- Exercise number-, the exercise explicitly or Both?

Regarding the titles on questions, 
Is better 

The author of the book, the chapter number and the exercise number.  
The exercise as explicit or informative as possible (not always possible tho :( ).
Both 1. and 2. (whenever possible).

?
One cons that I find with 1. is that if you don't have the book, then the title will be misleading and probably a waste of time when clicking. And a pro, if you have the book, then the search would be really easy (more easy than 2.) one just need to type for the author of the book, chapter, exercise, and done i.e. no need to type MathJax and check for the all the suggestions (which sometimes none of them have what one is looking for exactly).
See for example, for 1.
https://math.stackexchange.com/search?q=rudin+exercise+chapter+is%3Aq
Edit
This question first 
had

Courant John 4.6 16

then

Courant John 4.6 Problem 16 - Prove that $\int\int_R e^{-(x^2+y^2)}dx dy=ae^{-a^2}\int_0^{\infty}\dfrac{e^{-u^2}}{a^2+u^2}du$

and then

Prove that $\iint_R e^{-(x^2+y^2)}\,dx\, dy=ae^{-a^2}\int_0^{\infty}\frac{e^{-u^2}}{a^2+u^2}\,du$

A:

If you put the effort to properly write up a question, putting the extra bit of having a proper title should not be an issue.
Laziness is not an excuse.
Put the reference in the question's body, otherwise, stick to leaving the title informative for those who don't have the book at hand. If you plan on asking a question that only your teacher and classmates can immediately understand, just ask it in class or office hours.
Not to mention that this is helpful exactly in the case that every question would appear in a unique location through the literature. But do you know how many books have an exercise/theorem along the lines of "$B$ is a basis of $V$ if and only if it is a maximal linearly independent set"?
Putting "Book X, Theorem 1.2.3" in the title will not help you find previous questions, and it will not help others find your question in the future.
So until we change mathematical literature everywhere, let's stick with informative titles, yes?

A:

This is a good question. 
It depends on the exercise you want to ask. 
As you observed, writing the reference alone is less informative. On the other hand, one advantage of adding author + chapter # + exercise # in the title is that it provides precise context. It also helps to avoid the question being targeted as a duplicate mistakenly. An exercise X in book A and book B may have the exact same statement but depend on completely different sets of definitions. 
Moreover, some classic or popular textbooks are well-known. Some obstacles in the book when reading are common for many readers and thus they may have very similar questions. Adding the reference in the title makes the question especially more searchable and it helps to avoid posting further duplicates. 
Of course, there are very standard exercises in which adding references is not that important; at worst, it is a slight distraction. 

... no need to type MathJax and check for all the suggestions.

If you write your title after writing the post, you can copy and paste the part that you need from the body to the title. This would save a bit of work for you to write an informative title. But sometimes, writing the title first can show you a list of duplicates. If you need to type out a formula in the title, you would usually need it in the body anyway. 

