Resources:

sudo apt-get install ctags
ctags -R
ctags -R --exclude=*.js 
ctags -R --exclude=*.js . ~/.rvm/gems/ruby-1.9.2-p290/gems/
:ptag say_hi
:pclose
:tags
:tag
:h CTRL-T
:h CTRL-]
:h usr_29.txt 
set ignorecase