If sailing at Dartmouth ask on the dock if any of the other boats can spare a crew to help out - the dock at the Royal Dart is full of really helpful, friendly folk who'd be happy to help.
If you have time do some "dry pole" work. Construct a "rope" spinnaker, basically a long length of rope with three corners (one for the guy, one the halyard and one the sheet). Hoist it on the dock using the pole and go through the motions of a hoist, some gybes and a drop. Best way to learn and get the crew thinking about how to do it if all completely new to it.
Choose a day of light airs. Go out somewhere suitable and anchor the boat by the stern (i.e. stern to wind). Set, gybe and douse the kite when anchored. Sounds silly but it works, leaving you lots of time and spare brain cells to work out what's happening, without worrying about what you're going to hit. You can even do it with the book (or a print-out of this thread) in one hand!
I think that Ken has wussed out as usual - stuff this anchoring business, go fro broke and tie off to the end of a pontoon, that way you can get off and have a look at how things are looking, take a few photos, wander over to another part of the marina for a different view, get the expert advice and opinions of neighbouring skippers and generally get much more out of the exercise
Lots of good advice Clive but not much encouragement. There is nothing quite like being dragged downwind on the verge of disaster at speeds you never dreamt possible and once you've had a dose of the drug you just have to have more. You go for it and ignore the terrified screams of the crew but do make sure the wash boards are in place and the hatch locked shut. This ensures the crew stay on deck and if you broach the water stays on deck as well. Joking aside, once you've used a spinny you'll realise what a waste of time and enery it is to sail Goose Winged.