goto line

:12 ENTER

search and replace

:%s/foo/bar/g

view hidden chars

:set list
:set nolist

reformat tabs to 4 spaces

:set tabstop=4 expandtab
:retab 4

Convert endline

:set ff=unix
:set ff=dos

# vim: set expandtab tabstop=4 shiftwidth=4 softtabstop=4 textwidth=75

# quit
:q!
:qc

# include file
:r /path/to/file

Links
http://www.lagmonster.org/docs/vi2.html
http://vim.wikia.com/wiki/Search_and_replace