Chicago Comic Con Panels and Photo Op?

I am going to attend my first con in August. The main thing I want to do is get my picture with James Marsters. I see where you purchase the photo op but I was wondering are there specific times to get my pic? Since they are having so many buffy people this year I assume there will be a buffy panel so I want to make sure I have enough time to get my pic with James and get to the panel. Also, can you take any pics during the panels? When do they make the announcements for the panels or do you find out when you get there? I want to make a good plan of attack!! Thanks!!