2. Prepare For The Worst...
Speaking of historical precedents... As wonderful as many of humanity's achievements are, you have to admit that we have an instinct for war and pillage, and there's nothing to say that aliens won't be the same. Stephen Hawking has famously said that contacting aliens could have catastrophic consequences. The thinking is that, for an intelligent species to gather together the technology and resources to travel through interstellar space, there's got to be a better reason than to have a chat with the humans. Given that a lot of our current plans for space exploration centre around the potential to mine resources from moons, planets and asteroids, there's a very good chance that the the only way we could get aliens to visit our little planet would be if they wanted something that we have. Something like, say, water, gasses from our atmosphere or minerals. They could be eyeing up all of that lovely hydrogen in our sun as we speak. This "compete or die" instinct has been bred into us by Darwinian evolution and the chances are that a species similar to us will have grown up with the same kind of pressures (although it would be a hell of a coincidence if they also called it "Darwinian"). As the Cambridge professor, Simon Conway Morris, put it "if the cosmic phone rings, dont answer," it could be the last thing we ever do.