I'm gonna use this post to put all tips and tricks that I found.

configuration

set invlist  # see invisible characters

set tabstop  #specifies the width of tab character
set softtabstop  #when enabled, fine tunes the amount of whitespace to be inserted 
set shiftwidth  #determines the amount of whitespace to insert or remove using identation
set expandtab  #when enabled, cause spaces to be used instead of tabs