Having done it once (2004) I found bike fitness generally to be the best thing, plus press ups, three reps of 50 each day prior to the event. Don't over do it with the isotonic drinks - plenty of plain old water is best (should be plenty of that up there !!)
Enjoy the event, it's magnificent and a real priveledge to be a part of. I finished with an award on a nightmare score, but I finished and that's all that matters to me !!