These FAQs regularly suggest packages that will “solve” particular problems. In some cases, the answer provides a recipe for the job. In other cases, or when the solution needs elaborating, how is the poor user to find out what to do?
If you're lucky, the package you need is already in your installation. If you're particularly lucky, you're using a distribution that gives access to package documentation and the documentation is available in a form that can easily be shown.
On TeX Live-based distributions, help should be available from the
texdoc command, as in:
which opens a window showing documentation of the footmisc package. (The window is tailored to the file type, in the way normal for the system.)
texdoc can't find any documentation, it may launch a Web
browser to look at the package's entry in the CTAN catalogue.
The catalogue has an entry for package documentation, and most authors
respond to the CTAN team's request for documentation of
packages, you will more often than not find documentation that way.
On MiKTeX systems, the same function is provided by the
Note that the site texdoc.net provides access to the
documentation you would have if you had a full
installation of TeX Live; on the site you can simply ask for a
package (as you would ask
texdoc, or you can use the site's
index of documentation to find what you want. (This is helpful for
some of us: many people don't have a full (La)TeX installation on
their mobile phone … yet.)
If your luck (as defined above) doesn't hold out, you've got to find documentation by other means. That is, you have to find the documentation for yourself. The rest of this answer offers a range of possible techniques.
The commonest form of documentation of LaTeX add-ons is within the
dtx file in which the code is distributed (see
documented LaTeX sources). Such files
are supposedly processable by LaTeX itself, but there are
occasional hiccups on the way to readable documentation. Common
problems are that the package itself is needed to process its own
documentation (so must be unpacked before processing), and that the
dtx file will not in fact process with LaTeX. In the
latter case, the
ins file will usually produce a
drv (or similarly-named) file, which you process with
LaTeX instead. (Sometimes the package author even thinks to
mention this wrinkle in a package
Another common form is the separate documentation file; particularly
if a package is “conceptually large” (and therefore needs a lot of
documentation), the documentation would prove a cumbersome extension
dtx file. Examples of such cases are the memoir
class, the KOMA-script bundle
(whose developers take the trouble to produce detailed documentation
in both German and English), the pgf documentation (which
would make a substantial book in its own right)
and the fancyhdr package (whose
documentation derives from a definitive tutorial in a mathematical
journal). Even if the documentation is not separately identified in a
README file, it should not be too difficult to recognise its
Documentation within the package itself is the third common form.
Such documentation ordinarily appears in comments at the head of the
file, though at least one eminent author regularly places it after the
\endinput command in the package. (This is desirable, since
\endinput is a “logical” end-of-file, and (La)TeX doesn't read
beyond it: thus such documentation does not “cost” any package loading time.)
The above suggestions cover most possible ways of finding documentation. If, despite your best efforts, you can't find it in any of the above places, there's the awful possibility that the author didn't bother to document his package (on the “if it was hard to write, it should be hard to use” philosophy). Most ordinary mortals will seek support from some more experienced user at this stage, though it is possible to proceed in the way that the original author apparently expected…by reading his code.