He was notoriously bad about reporting his findings to other scientists, and many of his other defenses were flat our wrong(his argument based on the tides for example).
There wasn't much of an established practice of publication and peer review back in those days. Most often, people like Galileo just corresponded with like-minded people. Or sometimes published books. As for the tides, yes, he was off a bit there, but that's not what got him convicted for heresy. A few links, for those who may be interested:
The Crime of Galileo: Indictment and Abjuration of 1633. The heresy confession.
Trial of Galileo Galilei in 1633.
Letter to the Grand Duchess Christina of Tuscany. Galileo's opinion about science/scripture conflicts.
Ichneumon's excellent presentation of the issues. FreeRepublic post #31.