I don't have a degree in Spanish but I lived in Spain for 11 years so am a fluent speaker .

So first I will be friendly with him .For example how are you ,how was your day and etc. After I do that is I will teach him the subject that is Spanish and then when am done teaching I will say see you later and have a good day.In my opinion if you be friendly they will love to learn with the person that is being friendly that in this point is me .