If this is a 'bring your own project' type retreat, don't be too ambitious. At my first retreat, I was determined to get all the blocks for a queen sized quilt finished. I sewed and sewed and sewed and missed out on so much else. Slow down, enjoy the process, while walking to that ironing station, take the opportunity to look at other guests' projects and talk to them.
If you have an allergies, make sure that the organizers are aware. If you are attending with friends/relatives, do not feel that you have to spend every minute with them. This is an occasion not only to learn new things but also to make new friends.
And above all have fun!!