The actor - who plays Nicholas Brody on the hit drama - told The Hollywood Reporter that the writing team often don't know where the story is going.
"They're phenomenally talented and collaborative, as long as they know what the story is going to do," he explained. "Often they don't."
He recalled: "There was one incident toward the end of the first season, they didn't happen on it. I think genuinely they didn't happen on it in the writers' room until about episode five or six, and then they came to me and said, 'We think this happens'.
"I was like, 'What? What do you mean that happens? I'm that guy? I'm not that guy?' Then you realise you're a guy that's being written. So you roll with it."
Homeland will return to Showtime in the US on September 30. Channel 4 has picked up the rights to air season two in the UK, with a late 2012 broadcast planned.
Series exec Howard Gordon recently hinted that the show's second run will introduce "new antagonists".
"Season two is going to start about five or six months after season one ended," he revealed. "Carrie (Claire Danes) will not be in the intelligence service, and the world will be at a boiling point."
> Homeland adds True Blood actress Valerie Cruz
> Homeland casts Lost star Zuleikha Robinson for season two
Watch Damian Lewis discuss Homeland season two with Digital Spy below: