Sometimes it doesn't matter.
In my early days at the PD's office, I was assigned to probable cause/bond hearings. Normally, it's pretty hard to screw these up since the name of the game is to use them to find out what sort of information the state has, get witnesses to commit to their stories under oath, etc. The judge finds probable cause 99% of the time so the most important rule is to keep your client quiet. Most of my clients understood that talking at this stage would not help. However, I still remember one guy all these years later. When the police officer was doing his standard spiel on the stand, my guy kept raising his hand like he was in fucking school. Of couse, I told him to stop, but he had the judge's attention.
The exchange went something like this:
Judge: "Mr. Shuize, it seems as if your client wants to say something."
Me: "No, Your Honor, he does not."
Judge: "He's still raising his hand."
Me whispering sharply to client: "Put your hand down."
Judge: "I'm inclined to let your client speak. It's his right to testify."
Me to whispering sharply to client: "Put your hand down. Nothing good will happen if you talk now."
Judge to client: "Mr. X, do you want to testify?"
Client: "Yes, Judge!"
Young and naive though I was, I had enough sense to ask the judge to put it on the record that I had advised my client not to testify. Ten minutes later, he'd managed to turn one charge (somehow I remember it as a misdemeanor, but we wouldn't have been representing him unless it was a felony) into three more felony charges.
At the end of which I turned to him and said, "Well, are you happy now?"
He responded, "Yes, I am."
So I sarcastically shot back, "Great, then we're ALL happy."
The whole exchange was recorded by the mic on the table. A few months later, one of the senior attorneys came to my office and asked me if I remembered Mr. X. As he started reminding me of the client who had talked himself into 3 additional felony charges under my supervision, I thought I was going to get in real trouble. But he said he just wanted to tell me how much he enjoyed listening to the tape and hearing my frustrated "then we're all happy" comment from such a young attorney just starting his career.