1. If possible for lines, having chairs or benches where people can sit down while they're waiting in line for panels is extremely helpful!
2. Having line staff is critical. I'd say maybe one staffer for every hundred or so people in line, and one person at the very end of a line holding up a sign that reads "END OF THE LINE".
3. Try to keep folks who are mingling/loitering, but not in line for an event a good distance away from the actual line. A good distance away would be about 2-3 yards, just so anyone who needs to get through can do so without having to push their way down a hallway and so people can't magically insert themselves in the middle of a line they weren't actually in.
4. Digital Pre-Registration is absolutely critical to avoiding a "Linecon" scenario. How it would work is that, people would sign up online, print out a registration barcode, go to a registration booth on-site, scan their registration barcode, and get a badge printed right then and there. Gift bags can then be given out to folks at the end of the registration area for those who have gotten their badges. This greatly helps to expedite registration. That way, only the people who register on-site actually have to be in line.
5. I agree with Sramdi about a number ticket system for the gameplay events. That is a very good way to ensure that you don't have a swarm of people waiting for other people to finish when those same folks waiting in line could be doing other things.
6. A very important thing: Credit Cards are the modern way of paying for things. Every staff member who handles money of any kind should have a credit card reader.
7. Some of the entertainment, such as when The Primals came on stage seemed very rushed and awkward. I don't really blame anyone or anything other than a severe lack of rehearsal. It was kinda... uncomfortable for me to watch.