Aside from physical appearance Aliens are a lot like us. In fact, we are Aliens to them! Are there differences between them and us? Of course, but those differences aren't much greater than differences between the different races of Mankind.
[Note: I am speaking from experience. I have met Aliens numerous times, both through abduction and also Military/NASA contact.]
Furthermore, it's my belief that--as Souls--we have been in infinite existence and have actually been, at one time or another, everyone of those 'Alien' Races. I also believe that God's love encompasses each and everyone of those Races, including even the lesser animals of the Universe.
So, how should we act regarding Aliens? I believe we should be true to our Religions and offer friendship and love. Yes, even love! Often Aliens react to acceptance, friendship, and love just as we do. They return it and a true working relationship is established.
Will there be problems and even trouble and war. Of course! Just like humans have trouble and wars. And just as we try to avoid these conflicts we should try to avoid these conflicts with Aliens as well (survival may depend on it). This is why Capitalism and Trade work well to establish beneficial relationships where minor differences in behavior and Religion are overlooked.
[Note: If abducted show respect for the Aliens and their advanced te4chnology. Often this results in the Aliens showing respect for you.]
We are all DNA Creatures of God with much more in common than different.