RBP goes in seconds, seriously SECONDS so if it's 6:05am you will miss out because they are all gone before it gets to 6:01am
We had a great time with the standard Fantasmic packages, there was no "fighting for ground seating" like others have mentioned, it's all very civilized.
You line up in your group and start to enter, the area is huge so you lay out your cushions or a small blanket and sit and relax until the show starts.
Don't bring a huge blanket and sit two people on it. You'll be asked to pack it up, we saw two people doing this and it's not very polite trying to take up an entire area with a blanket when people need to fit in.
We got inflatable cushions and were very comfortable, we sat right at the railing which I won't do next time because it was freezing in November and we got soaked.