Big up for taking the course. As others have said it is one of the best courses BSAC provide.
Other than assembling the materials I would not spend too much time preparing. Just go with an open mind and put your preconceptions to one side. You are not there to perform perfectly, you are there to learn. Listen to the lessons, make your mistakes and take on board the critique. As I often tell my trainees, getting it wrong is half way to getting it right ;-)
Visual aids need to be affective and appropriate to the lesson. No point spending hours creating a PP slide for a dive computer if you can just hand a couple of computers round the class. If your students are dozing off as you put slide 37 on the projector, it is hardly affective. The very worse thing you can do is put up a PP slide filled with bullet points and just read what is on the slide. Really good PP presentations are quite difficult, particularly if you lack design skills. There is usually an easier way which is more affective.
There are times when PP is appropriate to support the lesson. I ended up using PP on my TIE and got a merit for it. The subject was Large Boats and dragging a 10m hard boat into the classroom wasn't really on. You can download the presentation if you want to try and work out what makes it affective.
http://dmz.mssystems.co.uk/files/tie-1.zip
Unless things have changed you may be allocated a lesson or allowed to pick your own. The coach on my ITC (IFC) had a number of lesson subjects and we were allowed to pick what we wanted in the order we were going to present. So the guy first up to the stand had the greatest choice of lessons.
Top Tip: don't plan anything for the evening of the course, you will be far too busy.
Have a great time.