Stick to the facts, and maintain control of the conversation.
Start with "the reason I called in here today is to discuss <issue>" and follow the formula the Redeye stated above.
Above all else, stick to the facts, maintain control of the conversation, and make it clear is more than a coaching or seek to understand.
A common pitfall when delivering a corrective action is falling into the "compliment sandwich" trap... That is, mentioning something good before and after the bad news is delivered. While it seems like a good idea, it can confuse the team member, overshadow the rest of the conversation, and loses the "formality" of the corrective action.