These FAQs regularly suggest packages that will "solve" particular problems. Mostly, however, the answer doesn't provide a detailed recipe for the job - how is the poor user to find out what (exactly) 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. For example, on a teTeX-based system, the texdoc command is usually useful, as in:
which opens an xdvi window showing documentation of the footmisc package. According to the type of file texdoc finds, it will launch xdvi, a ghostscript-based PostScript viewer or a PDF reader. If it can't find any documentation, it may launch a Web browser to look at its copy of the CTAN catalogue. The catalogue has an entry for package documentation, and since CTAN now encourages authors to submit documentation of their packages, that entry may provide a useful lead.texdoc footmisc
If your luck (as defined above) doesn't hold out, you've got to find documentation by other means. This is where you need to exercise your intelligence: you have to find the documentation for yourself. What follows 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 README file.)
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
to the .dtx file. Examples of such cases are the memoir
class (whose documentation, memman, is widely praised as an
introduction to typesetting concepts), the KOMA-script bundle
(whose developers take the trouble to produce detailed documentation
in both German and English), 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
existence.
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; however, it is possible to proceed in the way that the original author apparently expected...by reading his code.
This question on the Web: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=pkgdoc