I'm a longtime convention-goer (SDCC, NYCC multiple times, countless others...) but 2017 was my first D23 experience. My helpful hints for making it an enjoyable and not frustrating weekend:
- Expect LONG Days. Like starting before 5 a.m. and not ending until well after the convention has closed for the night (especially if you're planning on visiting the park too).
- Once the full convention schedule is published, try to identify the ONE thing each day that you'd be upset if you missed and plan your day around that. If it's one of the big panels (parks, live action, animation), expect that to take up at least half your day, if not more.
- As people have said, if you plan on being in the audience for the first panel in the large hall on the first or second day, then plan on camping out overnight leading into it. Other panels might not need a full overnight campout, but will still require a lot of line time.
- This will almost seem counter to my previous three tips, but if you're NOT going to one of the main hall panels, and there's nothing in the morning that you absolutely must do, consider showing up late. The morning lines moved very slowly as thousands of people piled into the convention hall and more people kept getting in line behind them. This is basically what happened to me on the first day of the show, where I showed up an hour before the show opened, and didn't get in until almost two hours later. On the third day of the show, I waited until about 2 hours after the show opened (taking advantage of the extra time to catch up on sleep), then literally walked right in -- and in fact walked right into Alan Menken's one-man show in the main hall, without waiting in line for that either.
Again, just know that you will NOT be able to do everything -- it's literally impossible, with so many panels happening simultaneously -- but with some planning and some patience, you'll be able to do a lot, and you'll have a fun time.