I remeber reading in the Valachi papers that Joe Valachi had a friend that was in another faction of the crime family they were in and that Joe told his friend to move out of his apartment if they were going to hit him and vice-versa, and this would be a non-verbal signal that he should have his head on a swivel. Don't remember if that's exactly what happened but it's more or less the gist.
I think you're referring to "The Gap". I remember reading The Gap giving Valachi advice that would keep him alive during the early years, especially after the Maranzano murder. There was a contract on Valachi because he was one of Maranzano's personal guard. IIRC, Tom Lucchese intervened on his behalf to keep him alive.
Also, prior to being made, he was asked by a crime boss to murder a friend but Valachi flat out refused.