It is also sensible to make your files are as portable as possible. To ensure this; they should contain only visible 7-bit text; and the filenames should contain at most eight characters (plus the three letter extension). Also, of course, it must not have the same name as a file in the standard LaTeX distribution, however similar its contents may be to one of these files.
It is also useful if local classes or packages have a common prefix,
for example the University of Nowhere classes might begin with unw.
This helps to avoid every University having its own thesis class, all
called thesis.cls.
If you rely on some features of the LaTeX kernel, or on a package, please specify the release-date you need. For example, the package error commands were introduced in the June 1994 release so, if you use them then you should put:
\NeedsTeXFormat{LaTeX2e}[1994/06/01]