If by "intelligent life" you mean lifeforms either A) not of sufficient intelligence to broadcast detectable radio/light signals or establish surface-level architecture (at least, within our solar system) or B) of an intelligence so advanced that they use a method more advanced / less traceable than light signals. Maybe they'd use neutrino beams, or maybe they've hacked quantum entanglement. Or perhaps they're just hermits.

Otherwise, I guess the most "intelligence" you could hope to find is something akin to dolphins. Anything of a higher level of intelligence would have deduced that their world is spherical in shape, and we can venture a guess that some of them would've had enough curiosity to start exploring upwards. The most I'm expecting to find in our own backyard is complex organic molecules. Even microorganisms would be a shock.

But for other solar/planetary systems, well, that's where things start to get interesting. Especially with how common extra-solar systems are, apparently (thanks, Kepler mission!).

Oddly enough, I ran into Alan Stern yesterday. He was giving a quick speech at a memorial service for one of the space engineering community's greatest minds that was recently laid to rest. :(

Edit: Ah, right, the other questions:

1. Re: Fermi's Paradox: What incentive would an alien race have to make their presence known to us? Benevolence? Were I an advanced alien, I would let Earth keep incubating without interfering until they'd proven themselves deserving of assimilating into any existing galactic order. Granted, this is all presuming intelligent aliens exist, and I'm not sure that they do.

2. Very likely, but not in our own backyard. Now that I think about it, I'll bet that the challenge of space travel is even more daunting for liquid-dwelling lifeforms, because liquid (in general) isn't as compressible as gas, and compressibility is handy for transporting finite resources during space travel.

3. When we develop the imaging capabilities, we should look for alien space stations in orbit near the cloud tops of large gas giants with large magnetic fields. A strong magnetic field offers protection against solar flares, cosmic rays, and nearby supernova explosions.