We post the raffle to the front page of ATP and it stays on the front page for several days. We also pre-announce them on the podcasts and we also discuss them on the forums ahead of time. The raffle ticket buying window is open for 3 full days.
We do the raffle each month, always on a Monday, and usually the 3rd Monday of the month. Hitting the homepage is the best way to keep up with the new and exciting things happening on the site.