 <p>How to debug a Rails application:</p> <ol> <li>Place a breakpoint somewhere in the app code</li> <li><a href="http://www.jetbrains.com/ruby/webhelp/running-and-debugging-2.html" rel="nofollow">Create Rails Server Run/Debug configuration</a> (or use the existing one if the project was created in RubyMine)</li> <li>Click on the <strong>Debug</strong> button in the toolbar</li> <li>Rails server starts in debug mode</li> <li>Browser with the app opens (or you open it manually if such option was disabled)</li> <li>Navigate to the page that will trigger breakpoint</li> <li>Observe the stack frame, locals, etc in the RubyMine Debugger pannel.</li> </ol>