I would recommend signing in and familiarizing yourself with all the steps beforehand. Get to the page where you can see the calendar availability and look for that refresh button. See how long it takes for the page to refresh, doing it a few times to check it. That'll give you an indication of how fast your connection is- and what you need to do come 8:59 AM EST. The day of, sign in by 8:45 or 8:50, carefully select your choice (occupy full villa, etc.) and watch the screen. Make sure you hit the refresh page at the right moment and make sure you know the date you want. Sometimes in the rush of excitement it is easy to click on the wrong thing.
I usually call at the same time, but am confirming my reservation by the time the rep is asking what I want. I always get a 9:00:00 time stamp; having a fast Internet connection helps.
Sptung- yes- but what does the resort offer? If all the villas are lock-offs, then you can call at any time. If only some are lock-offs, then a lock-off may not be available if you call later.