Don't over-think it! Recognize that your mind may be racing around, imagining all sorts of exotic situations and interactions if you're attending a workshop or "Tantric" event for the first time.
Once you are aware of your own projections and expectations, just let them run their course, and then try to stay open to receiving what is being given, rather than producing what you are generating.
Apart from that, come with as open a mind as you can!