There are two questions involved in communication with Extraterrestrials. One is the mechanical issue of discovering a mutually acceptable channel. The other is the more philosophical problem (semantic, ethic, and metaphysical) of the proper subject matter for discourse. In simpler terms, we first require a common language, and then we must think of something clever to say.
Golomb, Solomon W.
Word Ways: Vol. 1
, Article 5.
Available at: http://digitalcommons.butler.edu/wordways/vol1/iss4/5