If you're booking anything on DOC's site this season — Great Walks or otherwise — opening day can be tough. I run Schnerp (https://www.schnerp.co.nz), which monitors DOC's booking site 24/7 for cancellations, so I spend a stupid amount of time watching how this thing actually works. A few opening-day tips that aren't on DOC's tips page:
Each browser gets its own lobby position. When DOC's lobby opens, everyone is assigned a random queue position — and each browser counts separately. Open the booking site in Chrome, Safari, AND Firefox; that's three rolls of the dice instead of one. Going with mates? Get everyone in the lobby. Whoever gets through first books for the group.
Being early doesn't help, until it does. Your position is random, so showing up at 9:14 vs 9:29 doesn't matter. But you do need to be in the lobby when it opens. Wander in at 9:31 and you're behind everyone who showed up on time. Log in 15 minutes early and just sit there.
Cart first, pay once. A spot is held the moment it's in your cart. If you're booking multiple nights, add every one before going to checkout. People burn precious seconds paying for one night at a time and watch the next night go to someone else.
Stick around 30–45 minutes after. The half hour after opening is almost as live as opening itself. Sessions time out, people change their mind, carts release. If you didn't get your first choice by 9:35, keep refreshing till 10:15.
And if none of that works, that's the gap Schnerp fills. Cancellations come in all season long — last year most huts we monitored had at least one. Set an alert and forget about it.
Hope this helps you get the walks you're looking for!