I use the help2man program to generate them. You just need to write functions for the two command-line options '--version' and '--help' which show the version and some help text.
You don't need to (and shouldn't) do any fancy formatting of the text, but use double spaces at the begiining of the help lines:
echo " $0 [OPTIONS] FILE"
echo " --help show this help screen"
echo " --version show the version number and exit"
You may still need to fine tune it a little or adjust the formatting in the above function, but once you figure it out you have a formula for easily creating man-pages for any script without having to learn a lot of groff or using special man-page editors -which give varying results.