Close Encounters of the Third Kind

[lexico]

Suppose you faced an alien (extraterrestrial, not gaijin) for the first time in human history.
What would be your first attempt at trying to establish communication with this alien being ?
What would you try to do/say ?
How would you go about it ?
What would be the first things to go thru your mind ?

Some of you may recall the 1977 Steven Spielberg film, Close Encounters of the Third Kind.
Another review.
Yet another review. (Beware of ugly pop-ups, but the excellent review is worth the trouble.)
Some of you may even know that the MS standard greeting tune on boot up is a fast version of the human-to-alien communication tones played backwards.
But that was fictional. How about in reality ?

On a more serious note; if the alien were to speak an audible language, what would you find common with human languages ?
Naom Chomsky had suggested genetically built-in, innate linguistic predisposition for all human beings which allow infants (and youths) to pick up languages with relative ease. Human languages share certain features due to the common evolutionaly path and the common physical make up that makes us distinctly human. Of these characteristics, which ones do you think the aliens might share with us humans ?

note: I you who are reading this post is an alien, your response is also quite welcome, actually most welcome ! This is an open forum, and we do not discriminate against non-earth based, non-galaxy based beings so long as you comply with our forum rules and guidelines to bahave like civilized, considerate, non-violent, friendly beings !