Keep it Professional. Make class a formal, professional event. Formality will keep the "in class instructor" separate from the "after class friend or associate." Formality lets the students know they are being taught and their attention is required.
Never let students win a battle of personalities in a class. Remember: you are the captain of the ship and your control must remain inviolate. Find the ways to control or reshape strong egos.
Do not tolerate dishonesty, disloyalty, or brutality. Demand respect student-instructor relationship. Maintain strict dojang etiquette and protocol.
Command. Command attention by using a "command voice," something which Navy boot camp recruits are familiar. Speak with force from your diaphragm just as professional singers do. Relax your larynx and allow the force of the air to flow and sound the words, similar to the kiai. Sometimes you may need to sound each word as a kiai for emphasis. Tailor you voice to the number of students and the sound characteristics of the room. Speak distinctly to overcome an echo in the room. Tailor your pitch to the resonance of the room. Use of the command voice when giving commands gives your soft, caring voice more meaning when you use it. When directing students to do something, give commands. Keep your instructions simple and to the point. Do not ramble; it causes students to loose the mental and physical level they have built during class.
Be an Authority. Present information with authority. Present yourself as an authority on Taekwondo and present information as fact. Remember most people cannot differentiate between instructors who know what they are doing and instructors who act as if they knows what they are doing.