I always tell myself it will be fine. I sometimes even believe myself. And most times it is. In fact, almost invariably it goes well.
I am not sure what I'm afraid of. Maybe that they'll smell my fear and reject me. Or that they will refuse to participate. Or ...
There are some things you can do to improve your chances of getting a good outcome. Such as:
- Being genuine and caring about what you are doing.
- Knowing the participants (especially their attitude to what you are doing).
- Keeping your introduction brief and relevant.
- Finding the balance between 'showing off' and 'communicating your credibility'.
- Getting them to do something worthwhile. (You might need to explain why it is worthwhile.)