If you are going this year, grab the Royal Show app, it's actually handy - particular things like an interactive map from your position to the nearest toilets. Or guiding you to specific locations and pavilions.
Grab the Crowd Canvas app as well, if you are staying for the fireworks. They'll recommend over and over if you are there, but with thousands of people hammering the tower(s), downloading an app is hard. It's neat - the app takes over your phone flashlight and the crowd has synchronised flashes as a part of the event.
If going with kids, take a photo of each kid when you arrive. With the clothes they are wearing. If you lose a kid, you can give the police/organisers a photo of the kid as they are today. It'll make a huge difference. Also, teach your kids your phone number. That's not just limited to the show, though.
Check the events of the day. If you want to see woodchoppers, make sure you know when that is happening. If you want to see the duck races or dog jumping (and you really do) check when those events are happening. Again, the Interactive map on the Royal Show app is your friend.
The fireworks show is great. I thought it was better than the last Skyshow. The fireworks are just in front of you.