Chances are, if you meet an alien, it will look nothing like you. It won’t understand you, and you won’t be able play charades with it.
It won’t be a green-haired humanoid in a bikini. It might not even have arms; it might not even have eyes.
The only hope you have for communication is to use the universal language of math and science. After that, you just have to worry about being assassinated.
Below is a crash course (and probably my favorite infographic) on how you should react if you are the one to make the proverbial first contact with extra terrestrial intelligence. Although the message has a humorous slant, the actual scientific content and the social/political insight into how this could possibly go down is certainly “I have a degree in physics” level stuff.