Two Mac developers have created an alerts service, which you can sign up for free right now, that will let you know the very moment that tickets go on sale for this year's WWDC in San Francisco. Just put in your cell phone number, send back one code for verification, and then you'll get a text the instant tickets show up, which should give you a nice head start on making sure you get in the door for the conference.
There's also a Twitter account to follow if you want something that might get you a little less spam, but the makers of the alert system say they won't forward your details to anyone or misuse the list at all, so if you trust them, it shouldn't be an issue. Obviously this service is being seen by a ton of people, so I'm not sure how much help it will actually be, but any heads up is better than nothing. If you're planning to try going to WWDC this year, good luck!