title: where to find documentation on how to develop (rails 3) helpers
body: <p>I may be blind but I can't really find any good documentation on how to write helpers for your own views in rails 3.
  The kind of answers I'm looking for is:</p>
  
  <p>I have a partial view (say shared/_error_messages.html), where should its helper go, how should I name it, which are the conventions?
  How to pass local variables from the view to the helper and vice-versa?</p>
  
  <p>Yeap, so let's say from the basics...
  Thanks in advance</p>