This answer focuses more on minimalizing the code, rather than finding the source of the problem, as the top-voted answer does. It is intended to be concise and hands-on, but digestible rather than exhaustive. Suggestions for improvement welcome!
Here are some strategies for reducing your code, which will help you get better and faster answers, since it ...
There’s a new package on CTAN called mwe, providing some features for creating MWEs. This is the announcement text:
mwe provides several files useful to create a minimal working
examples (MWEs). A mwe package is provided which loads a small set
of often used packages for MWEs. In addition several different images
are provided which will be ...
TeX.SX (and all other networks on Stack Exchange) is a Question & Answer (or Q&A for short) site where users ask questions, which are then answered by community members. This structure is the fundamental building block for the site. The top entry of every post is the question, while answers are given below it.
Here is what the FAQ mentions regarding ...
In my experience, the OP does not always choose a title relevant to the problem s/he's facing. Example:
Tex doesn't work
A poorly chosen title is, of course, forgivable in many cases; the origin of the problem may not be obvious.
However, someone posting an answer that solves the OP's problem, or any subsequent visitor to the page who is savvy enough, ...
Proposal for Acceptable:
Updating code in old answers following software updates (e.g., a new package version)
Provided that the original code is preserved, to facilitate users with older versions and to show the effort of the original answerer.
See also Updating an old answer when my knowledge improves, or a package is updated.
I think I could add prof. van Duck's tutorials.
Section 3 Asking effective questions on TeX.SE of his first article in TUGBoat 38:3, 2017 explains how to build an MWE.
Section 3 How to format a post in TeX.SE of his third article in TUGBoat 39:3, 2018 explains how to format your question.
I also think that (at least) one answer to a question must be simple, if possible. That is, use existing packages as much as you can rather than resorting to makeatlatter and makeatother type hacking. See the question Is it still worth it to learn TeX?.
(Herbert is one person who is very good at providing simple answers in the above sense.)