When James Cameron and 20th Century Fox announced Avatar Day two weeks ago at Comic Con, the idea was greeted with great enthusiasm, but some confusion. Presenting a long Avatar sneak preview for free at IMAX 3D theatres sounds like a great idea, but how will the promotion work in practice? It’s a great way for (potential) fans everywhere to see what six thousand saw at Comic Con, but the logistics seem daunting. Now details emerge; they’re after the break.

The LA Times has some new specifics. On Monday, August 17, Fox will give away tickets on a first-come, first-serve basis through the website avatarmovie.com. Tickets will be available beginning at Noon PST (3pm EST), so you’ll have to be ready to click right then, as even with more than a hundred participating theatres (around 70 in the US) the tickets will go fast. Will you be able to score more than one or two tickets at a time? We don’t yet know, but expect a severe limitation on tickets per user. (And start taking odds now on what they’ll go for on eBay by Monday evening.)

The screenings will take place at 6 and 6:30pm on Friday, August 21. The presentation will begin with an introduction from James Cameron, after which will follow sixteen minutes of footage, including some stuff not shown at Comic Con. (The LA Times says sixteen minutes, which contrasts the originally announced 15 minutes. I’ll update to clarify when I know if the presentation will be 15 min of footage and a one-minute intro, or something different.) The Avatar trailer will also hit theatres that day, but the IMAX presentation obviously offers a better look at the visual fireworks Cameron has assembled for his first narrative feature in twelve years.

Avatar Day will also see the public release of the trailer for UbiSoft’s video game based on the film, and the designs of all Mattel’s toys. (One of which, showing Sam Worthington’s Na’vi avatar, was recently leaked and quickly C&D’d away.)