A post on quacking like a duck
Try to conform to ruby idioms
Normalize parentheses in Ruby snippets

Personally, I follow something like the Weirich Rule[1] to determine when to use parentheses:  I use them to indicate whether the return value from the call is significant.  I'm not in the majority.  ;>

[1] http://onestepback.org/index.cgi/Tech/Ruby/BraceVsDoEnd.rdoc
Use guard clause, add explaining variable
typo
drop explicit return (everything's an expression)
Example code doesn't actually raise an error ;>
clean up
Add thanks