Reddit mentions of First Big Crush: The Down and Dirty on Making Great Wine Down Under

Definitely be prepared for wetness, coldness and exhaustion at the very least. You might also want to try reading this book, written by a guy who worked the harvest in New Zealand: http://www.amazon.com/First-Big-Crush-Dirty-Making/dp/145161327X

Really the most important thing I found, though, was to assume nothing and to ask questions – even if you're 99% sure how to perform a particular task. Until you've done something 10 times (rack a tank, do a pumpover, etc.), there's the possibility you could get it wrong and cost the winery insane amounts of money. So it never, ever hurts to ask, even if you have the slightest hint of doubt about a job you've been charged with. Remember, too, that the bosses also become exhausted as harvest drags on, and they might accidentally give you conflicting instructions. Just ask for clarity if you're not sure.

Oh, and also be prepared to have the time of your life. I did two harvests several years ago, and I miss it dearly.