This is an extremely good and interesting question!
Life on Earth is made up of carbon and the reason for this is because a carbon atom is a really good building block for complicated structures. If life elsewhere has evolved from the same chemicals in the same way we did it too will be made from carbon there is a possibility that it looks something like us. Although I am a firm believer that life could have evolved in a different way and is made of a different main component.
However, I think if we find life we may be a little disappointed. I think it will only be bacteria, or something not quite as intelligent as us. I think if there is life out there that is more intelligent then it would probably have found us by now, or at least sent us a message!
It is a very interesting question, and I really do not know the answer. It is really very hard to imagine life that is different to what we have on Earth, we are so used to thinking of four legs, heads, eyes, etc. It would comlpetely depend on what the planet with life on was like, and how best animals could survive. I think my biggest hope is finding a planet with alien life on it, it would be the most interesting thing I can think of happening to mankind.
No I don’t think so. Even if life had got beyond the single-celled stage into plants or animals, there are many factors that would affect what the lifeforms looked like (gases in the atmosphere, the strength of gravity, etc.). And even if the planet was exactly the same as earth, life may evolve very differently. Evolution is quite hap-hazard in how life turns out, especially which species survive mass extinctions. Often it’s just a matter of luck.