Behind the scenes for iPhone app developers is the Apple backend system called "iTunes Connect". It's another world that most people never see, but app developers get to become pretty intimate with it as this is where you create the certificates you need, upload code, fill in all the information that becomes your entry in the App Store, screen captures, and on and on.

As Apple describes it, "iTunes Connect provides tools to help manage your content in the iTunes Store."

Now, let's suppose you've logged in to your account and are looking at the main screen. There are a bunch of options there, and you probably gravitate automatically to the "Sales/Trend Reports" link, but look a bit further down.

See it?

There's a link called "Request Promotional Codes". That's what you want:

Click on it and you'll be asked how many codes you want to generate:

I'm going to just produce one, so that's what I enter (notice that you have a max of 50 for each version of each app), then click "Continue".

Now you'll be presented with the "APP STORE VOLUME CUSTOM CODE AGREEMENT". Read it (or skim it, or skip it, whatever) and choose "I have read and agree to this contract" and click "Continue" again.

That's it. Click on "Download" and you'll get a small text file that contains the specific code you want to send the other party. Once you've done that, if you want to help them learn how to apply a download promo code to get an otherwise pay app from the App Store, check out: How to Redeem a Promotional Code in the iPhone App Store.

Good luck!