Just because a question contains the words "best practices", IMHO it is not always the case that it "refers to the technique that works for most people in most situations", as Thomas Owens wrote (nevertheless I think his answer is very good). One has to read and understand the full text of the question, check if the author makes reasonable restrictions to the scope, and if he has a real-world problem to solve (and if not, the question should be closed, of course). So asking a question like
I am in situation X, having problem Y and no clue how I can solve it. What could be the best practice to approach a solution?
can be fully acceptable. I think what @gnat wrote in a comment above hits the nail on the head - try to imagine how the question would look like with "best practice" words removed. I think that is a good test.
Furthermore, I think that a too specific restriction of the scope to a personal situation of the author decreases the value of a question as much as a too weak restriction of the scope. For example, by restricting something to a specific programming language when the problem itself is not language specific. Good answers can be applied to a wide range of cases, thus questions which define enough restrictions to be answerable, but not more, can actually encourage such answers.
So my opinion is:TLDR; it depends, there is no "simple criteria", taking the time to read and understand what the author asks is the only valid way to make a decision.
EDIT: due to the comments - yes, it is true, "best practice" has become a buzzword, often triggering a "close reflex". So my suggestion is: when a question passes the test that it still looks good with the "best practice" words removed, those of us who have enough rep to edit the question should consider to rephrase the question slightly, avoiding the buzzword.