I've found that with some games I'm able to pull the direct address out of the JS source, but with others -- flash games for example -- I have not been able to find a reliable way to ascertain the source address.

The source address is convenient in that it removes all of the obfuscating wrappers and puts the game into the immediate scope of the browser for hacking.  Better still, it allows you to play the game in a larger field and eliminates the unnecessary crap that Kongregate likes to put around the game frame.

Could someone please show me a reliable methodology for pulling this information?

Thanks.

you can also use adblock plus and pretend youre gonna "block" the game, but just grab the link instead.

but if its some shitty game that has a pre-loader swf, charles or fiddler is the way to go

Hm the link is usually right in the source code of the games page.
 

 new GameIframe({"iframe_url":"http://ninjakiwifiles.com/Games/gameswfs/sas4_kong/sas4.html"

Looking for "iframe_url" should give you the link.