I've played a couple of adventures that I had played/DMed some time before. In most cases, I look for legitimately different (or sometimes wrong) courses of action and suggest them. I never use prior knowledge to my benefit, and I always let the DM know in private that I'm a veteran of the game.
My best roleplaying has happened in a module where I knew that my suggestion was to follow a major red herring. I was pretty convincing, too. When the other players joked with me about what a stupid mistake I made, I sat there and took my lumps while the DM grinned evilly.
My best roleplaying has happened in a module where I knew that my suggestion was to follow a major red herring. I was pretty convincing, too. When the other players joked with me about what a stupid mistake I made, I sat there and took my lumps while the DM grinned evilly.