Question: In the scene where Tommy believes he is being made, right after he walks into the room you hear him say "Oh no!" right before he is shot. Tommy obviously realizes that he was set up. However, what is it that he sees in the room that tips him off?
Answer: A man being 'made' is an event shrouded in ceremony. The top people in the family are there, among others to congratulate the new soldier. Tommy walked into an empty room.
Just as others have pointed out, the film implies Tommy realised something was wrong the moment he walked in and saw the place was empty...no other "made men" there for the ceremony. However, I always wondered why he hadn't caught on to what was happening when he saw there were only a couple vehicles parked out in the driveway.
Answer: Either the fact that the room was empty (being made is a big ceremonial event with many people) or he felt the gun pressed against the back of his head right before they shot him.
Answer: There should have been more people waiting for him.
Answer: Wasn't the floor covered with a plastic sheet? That would have given it away.
Or it was a floor with no carpet (tiled, I believe)...easier to mop up.
Answer: He was expecting a crowded room full of friends congratulating him. Also it was common knowledge among the mafia that being walked into an empty room when you were due to be made meant you were about to be executed, so Tommy likely knew he'd met his end just moments before the shot.
William Bergquist