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If you are the passenger, you are not required to do anything until the officer asks you for your ID. And my recommendation is that you do exactly that - nothing. Just sit there quietly and let the officer go about his business with the driver.

Some officers are more jumpy or more suspicious than others. They may take it wrong if you even start to say anything, thinking you are trying to threaten them, convince them to give a break, etc. It is best to not get involved until they involve you. And if you come up on a DPS trooper who approaches from the passenger side, you will notice that this is true for them too generally. They will talk with the driver and almost ignore the passenger other than a polite greeting.