If you want to blog about GUADEC and tell everyone that you’re going or speaking there, you can find the badges (and the slide templates) on the website.
There will be slots for unscheduled talks and discussion panels during the core days. You will have an opportunity to propose a topic in the morning which other attendees can +1 if they are interested in it. At 16:00 on Friday, 13:30 on Saturday and 16:00 on Sunday, the most popular talks will be posted to the schedule board, so make sure to check back regularly!
Lightning talks will take place on Sunday the 14th of August, you will be able to sign up on the day!