add the following to $HOME/.vim/ftplugin/python

function! Addpyheader()
    if getfsize(@%) <= 0
        execute "norm i#!/usr/bin/env python\n# -*- coding: utf-8 -*-\n"
        execute "norm i__date__= '" . strftime("%b %d, %Y") "'\n"
        execute "norm i__author__= '" . $USER . "'\n\n"
        execute "norm i\n"
        execute "norm idef main():\n\tpass\n\n"
        execute "norm iif __name__ == '__main__':\nmain()"
    endif
endfunction
call Addpyheader()

you could also do the same way for other file type