Know the company, know what the job involves, find out what you can about the aircraft.
Have some sensible questions in mind, think about possible answers to the 'Why do you want to work for us?' type questions.
Possibly answers to 'Give an example of when you .... acted well in a team.... , .... got a job done through good judgment.... , .... held a position of responsibility.... , .... handled a crisis situation.... , etc.
That said, small companies tend to be fairly friendly - they mainly want to see that you know what you're letting yourself in for and that you'll fit in well. Don't be afraid to get a bit of banter going so that they think you're a nice guy.
Above all, be yourself, they'll smell bullsh!t a mile off....
Good luck.
Troy.