What makes a good title?
Good titles should unambiguously tell the user what they are getting into before they click on it. The goal is to attract the attention of those people who have the expertise to answer the question or may be interested in an answer, while not wasting the time of readers who don't care. Perversely enough, a good title might decrease the number of views, but should increase the average quality of interaction (as measured by time spent reading the question, ability of the reader to answer, and/or other folk having a similar question).
Good titles will generally consist mostly of nouns, verbs, and maybe a preposition or two (where one might regard an expression like $x = y$ as a SVO sentence or sentence fragment). Adjectives and adverbs should be few and far between, as they typically don't add much in the way of content (there are exceptions, particularly when such words are used in a technical capacity, e.g. a question about a "hard integral" is very different from a question about "hard analysis").
Good titles should quickly get to the point of the question. Ideally, a brief version of the question should be stated in the title. Because this website is about asking mathematics question, good titles will generally (though not always) include notation. Notation should be included, and should be typeset correctly, whenever it is appropriate.
Good titles include enough detail about the context surrounding the problem to provide signposts for potential readers. For example, the expression "$x^2 + y^2 = (x+y)^2$" will mean one thing if the title makes it clear that the problem was encountered in grade-school algebra, and another if accompanied by a phrase such as "freshman's dream" or "field of characteristic two". Thus a good title for question about this identity should include something about the material being studied. Other context which might fit into a title are a indications of the asker's level of knowledge, the general field they are studying (particularly if tags are insufficient), a text author (there are a large number of questions on MSE with titles containing some variation of "Theorem X from Baby Rudin"), or the provenance of a competition problem.
To build an example from something I encountered today, let us suppose that I have the following question (which is likely an appropriate question for MESE, but that isn't really the point):
Today, while helping my daughter with her remote-instruction schoolwork, I discovered that they students in her second grade class were being taught to solve linear equations in two variables using a method involving colored bars. The teacher's notes refer to this as the "bar model", but there is no explanation for how it works.
My daughter seemed fairly proficient with the technique, hence it went by too quickly for me to parse what was going on. It seems that she was using various bars of differing length (or color, maybe?---she seemed to be insistent on using different colors of whiteboard markers in particular way) to represent known and unknown quantities in a system of equations. The way in which bars were "stacked" or "concatenated" seemed important, though, again, my daughter worked through the problems faster than I could discern the pattern.
Does anyone know what this method is called, and can anyone explain how it works or point me in the direction of useful references?
So, what title should I give this question? A few possibilities include:
What is this crazy thing my daughter is doing?!
This title is less than useless. It gives the reader no idea what the question is about, and is, at best click-bait. Moreover, it editorializes (via the adjective "crazy"). My guess is that nearly every click on this title will be quickly followed by the closure of a tab or a user hitting the back button.
Can someone explain this technique for solving systems?
This title is better, but still leaves off a lot of context. What is "this" technique? Who is solving these systems? What is the level of student? The basic question is in the title, but there is no context to orient the reader (aside from a vague reference to "solving systems").
What is the "bar model" used by an 8 year old to solve systems?
On short notice, this is about the best I can do. The phrase "bar model" is important context (it was on the teacher's slide, after all), and the inclusion of my daughter's age tells the reader that a tenured professor with research in systems of nonlinear PDE probably doesn't care to click through, while an expert in grade-school education immediately knows that they might have an answer.
 For technical reasons, there is a small downside to including MathJax in titles: questions with MathJax'd titles cannot appear in the "Hot Network Questions" list, because the MathJax renderer is not loaded for every site in the network. To avoid ugly code in the titles of questions rendered on other sites, such questions are excluded from the list. However, this technical concern about how mathematics questions are advertised to the wider non-mathematics community should be a minor, secondary concern (in my opinion).