RE: trainee etiquette
While nothing is required, we provided a Home Depot gift card to show our appreciation.
Bottom line: it's whatever you are comfortable with. I felt that our instructor gave up a lot of his flying time to help us out. I have instructed in other venues and know that student success is all the satisfaction I need, but a little something extra, if you really appreciated his/her services (cookies, gift card, etc.) won't be refused.
Jack