Here is a nice, brief article I came across on teacher's etiquette. It is specifically designed at Islamic teaching, like madressah, etc., but even though I teach math to non-Muslim students much of it still applies. I have also added at the end something from Imam Ja'far Sadiq (as) I found on the same subject.
Shahîd ath-thânî, Shaykh Zaynud-dîn b. `Ali b. Ahmad al-‘Âmilî (d. 965 AH) has complied a book on the significance and etiquettes of learning and teaching in Islam. The work Muniyatul Murîd is higly beneficial for teachers and students of an Islamic school. Shahîd ath-thânî has listed thirty etiquettes that a teacher needs to follow while s/he is in a classroom with students.
Following are some of points for we need to consider implementing. We pray to the Almighty Allah ifor success and acceptance. 1. The teacher should be dressed neatly and respectfully with complete awe and reverance. White dress is recommended for it is the best dress.
2. When going to the class read the du`â taught by the Holy Prophet . I begin in the name of Allah, the Beneficent, the Merciful. O Allah, bless Muhammad and his family. O Allah, I take refuge with You from misleading or getting misled, making mistakes or being made to make mistakes, doing wrong or being made to act wrongly, and (from) acting ignorantly or being made to act with ignorance. [O Allah] Mighty is Your protection, Holy are Your names, Sublime are Your praises, and there is no god besides You. In the name of Allah, sufficient for me is Allah. I rely O Allah, and there is no power and strength except with Allah. O Allah, strengthen my heart and let truth appear on my tongue. O Allah, bless Muhammad and his family.
3. At the beginning of the class or whilst heading to the class have the intention (niyyah) of teaching and spreading the knowledge in order to disseminate Islamic sharî‘ah, conveying the rules of religion and increasing of knowledge through remembrance.
4. Greet, i.e. say salâmun ‘alaykum to all those present.
5. Begin the class with a brief recitation from the Holy Qur’ân. Then pray for those present, for all Muslims and for your self. Also, say a short khutbah (sermon) that includes taking refuge from Shaytân, praising Allah, salawât on the Prophet and his family, and praying for scholars.
6. When teaching, sit with tranquility, dignity, humility and modesty. Facing the Qiblah is recommended. The Prophet fhas said: the best gatherings are those in which people sit facing Qiblah.
7. Avoid excessive jokes and laughing for that reduces ones self-respect.
Imam Sadiq (as) said,
"Your teacher has the right over you that you should honor him and pay him respect in different assemblies. You should be very attentive to his words. you should not raise your voice above his. if anybody asks him a question, you should not give its reply. You should not converse with others in his presence and you should allow the people to benefit from his knowledge. You should not speak ill of anyone before him. If anybody speaks ill of him in your presence, you should defend him. You should conceal his shortcomings and bring his virtues to light. You should not associate with his enemies and should not dispute with his friends. If you act on these lines the angels of Allah will testify that you have paid attention to him and have acquired knowledge for the sake of Allah and not to attract the attention of the people.
And the right of your pupils on you is that you should realize that in granting you knowledge and opening its path to you, Allah has appointed you to be their guardian. In case, therefore, you teach them properly and do not frighten them and are not furious with them, Allah will, through His kindness, increase your knowledge. But if you drive the people away from knowledge and, as and when they approach you for it, you frighten them and get annoyed with them, it will only be appropriate that the Almighty Allah may take away the light of knowledge from you and may degrade you in the eyes of the people."