I have recently read many articles about where life in the universe is likely to be found and what are the preconditions for it. This is a complex subject stretching over many disciplines, astrobiology first, and it is not an accident organisations like NASA devote so much time and efforts.
I am going to write a few articles on The Earthian Hivemind in the coming months, covering the following – related – topics:
– Theories about life – what is life, and what has generated life in the first place. (Hint: this is more controversial than it looks like at a first glance).
– The most likely place / environment where we might find it. 
– Is there any world nearby that qualifies for life? (Hint: Moons are more likely than planets, for all we know. Europa, Titan and Enceladus looks like good places to start with).
– Which kind of (alien) life we can reasonably expect to find.
I think these are the most important areas to cover – if there’s anything I’ve overlooked, please do let me know.
In the meantime, this article by Stephen Hawking, Life in the Universe, it’s a good introduction, even though overall pessimistic in its conclusion, to this truly fascinating subject.
“What are the chances that we will encounter some alien form of life, as we explore the galaxy. If the argument about the time scale for the appearance of life on Earth is correct, there ought to be many other stars, whose planets have life on them. Some of these stellar systems could have formed 5 billion years before the Earth. So why is the galaxy not crawling with self designing mechanical or biological life forms? Why hasn’t the Earth been visited, and even colonised. I discount suggestions that UFO’s contain beings from outer space. I think any visits by aliens, would be much more obvious, and probably also, much more unpleasant.”