Since this is the Comics Section, I'll assume all questions are in regards to the Marvel comic and not the cartoon series, where the answers would be very different.
lilboo said:
how are transformers "born"?
Well, they're either built or born through a sort of "budding". Mostly, only first-generation Cybertronians did the "budding" thing. Transformers can be built, but the only way they can be granted sentience and there for "life" is by using the Creation Matrix, which started out as just a computer code but eventually turned into the Matrix of Leadership as we recognize it.
if they've never seen earth or whatever, how do they know to turn into helicopters, firetrucks, ambulances, etc.?
Being sentient robots, they created the whole transformation-thing as a means of self defense and espionage during the war. In the early Marvel comics, the Transformers on Cybertron (before having been to Earth) are shown transforming into very alien-looking vehicles. They didn't start turning into helicopters and ambulances until they established contact with Earth. Now, some fiction has them turning into Porches and what-not on Cybertron without having been to Earth, but that's mostly out of bad writing.
did transformers start out as comics published by marvel?
The Marvel comics preceeded the cartoon by only a few months, but both were developed simultaneously.
why are autobots and decepticons enemies?
Difference of opinion, essentially. The Decepticons want conquest and the Autobots want peace. The cartoon has it a bit deeper, with the Decepticons having been built as warrior drones and the Autobots having been built as slave drones, but that's a different continuity.