We're in favor of understanding tween-speak. Not only is it as interesting as picking up a second language, but it will save you a lot of trouble when it comes to keeping tabs on your tween's state of mind.
That said, every embarrassing parent should know this: It's one thing to understand what your tweens are saying in the backseat as you shuttle them to and from the movie theater. It's another thing entirely to repeat it.
Do not, under any circumstances, shout "Holla!" to greet your tween. Try to actually laugh rather than say, "LOL." And, if you make a mistake, refrain from muttering, "My bad." If you're texting, steer clear of tween abbreviations, too. After all, AYSOS? (Are you stupid or something?)