How can passengers help in the cockpit in an aviational emergency? During an emergency solely related to aviation (ie not a medical situation), suppose that some airline passenger believes that he/she can help in the cockpit. Since the cockpit door is locked for security, how can he/she volunteer their services and enter the cockpit to try to help? I am guessing that someone with minimal flying experience (such as an amateur gamer of Microsoft Flight Simulator) can help. 

This question presumes the ability of airline passengers to help. Here is a real-life example: According to the Mayday episode on Air France Flight 447, while attempting to recover from a stall, the first officer pushed his yoke up (wrongly), while the reserve first officer pushed his yoke down (correctly).  This opposition in pushing nullified each other and the plane continued its fall in its stall.

The captain was out of the cockpit at the start of the stall. He returned afterwards (I don't recall exactly when), spent some critical time surveying the control panel, but didn't apprehend the problem in time. Might a passenger have helped to perceive the problem (without spending time examining the instruments)?

Please feel free to edit this post; I'm not an expert on aviation.
The short answer is to sit down, shut up, and stay the heck out of the way.  That's what I would do.  If you can quietly help the one or two people sitting next to you do the same, you're doing your part.

Seriously, the last thing the flight crew needs in a flight emergency is extra distractions from passengers - especially those without directly relevant experience (e.g., an off duty airline pilot commuting home).

Less seriously, it's a common fantasy/daydream among private pilots that some weird emergency results in them taking over the controls.  Pre-9/11, I had the opportunity to try landing a 747 in one of the airline's full motion sims.  (I have zero relevant experience in flying something that big).  On the first landing, all the big pieces came to a stop on or near airport property.  On the second attempt, I think I got most of the pieces to come to a stop on or near the runway.  I doubt many people would have survived either attempt.

My plan if this would ever happen in real life is to get on the radio &amp; demand that an instructor tell me which buttons on the autopilot to push.  If successful, I'd then go buy a lottery ticket before the crazy luck wears off :-)