Do we know how to look for extra-terrestrial life?

On Mars, the Curiosity Rover is investigating whether the planet has any signs of life or any signs of past life.  The other day, NASA announced it found a planet orbiting a binary star system in the so called "habitable zone."  That is...seemingly habitable for us.

But should we assume life can only exist if it is like us?  Could it be that life on earth exists as it does because life on earth is uniquely adapted to living on the earth?  Could it be that elsewhere, life could exist uniquely adapted to conditions on that planet?

We know that 70% of the earth's surface is covered with water.  We also know that up to 60% of the human body is made of water and the brain itself is 70% water.  Is this coincidence?  Or is it that our makeup includes a lot of water because the earth has a lot of water?  Do we exist in the form that we do because this is the form that is suitable for living in the atmosphere, conditions, and temperatures of the earth? Is the size and shape and speed of rotation of the earth a distinguishing factor too?

Could another form of life be adapted to conditions on another world is the real question here though.  So for instance, if life existed on Saturn's moon Titan, what would it look like?

I wrote about Titan recently, noting that Titan had hydrocarbon lakes and rain.  It's not water...but if life existed on Titan, isn't it likely the makeup of that life would include the liquid hydrocarbon (like methane) native to that moon?  Titan is a cold place...but cold to who?  To us?  If life did exist on Titan, then presumably the life would be capable of living in the temperatures on Titan naturally.

So is there life on Titan?  No one has seen any people walking around on Titan, so if there is, it isn't immediately apparent.  But if it did exist on Titan, then what would it look like?  What would a body made up of substances native to Titan and capable of living in frigid temperatures look like?  How big would it be? Would it even look anything like us?

Maybe it looks like nothing because nothing is there.  But Titan is just one example of a world in a universe of galaxies full of planets and moons.  Should we always be looking for something like ourselves on a world that is not our own?  Do we even know how to look for life on a world that is not our own?

If you want a Windows PC, you wouldn't look for it in an Apple store.  But you can still find technology products in an Apple store that are designed to be sold in that store.  Perhaps we should be looking for signs of life that fit the environment of where we are looking instead of looking for signs of something that looks like life on earth.