A couple things I haven't seen in the posts above yet (or that I missed)...
Know where the sun is. You can't save a nice rocket picture that is essentially a silhouette, I don't care how much dynamic range your camera has.
Turn image stabilization off if you're on a tripod, or select the proper IS mode for tripods, depending on the lens.
Select the smaller focal distance setting if your lens has one, instead of the full range.
Take several shots before the launch to verify settings. Nothing is more frustrating than trying to take a picture only to realize the 2 second delay timer is still on from taking astrophotography shots the night before. Or so I've heard.
Have a spare battery and memory card in your pocket, not in the car, and not in the camera bag you left on the other side of the flight line before you walked to where the sun was at a good angle.
Never close the door on an empty hole, be it a memory card slot, or a battery compartment. NEVER. If that means letting the camera sit on your desk overnight with the door open, do it. You won't forget to take the battery off the charger in the morning, or the memory card out of the computer.
Don't get so focused on the rocket that you forget to consider the background. If you move 10 feet to the left, can you have a nice green background of distant trees that will make a nice bokeh instead of a car, port-o-jon, or pop-up tent at a much closer distance that will just appear as a blurry, out-of-focus distraction?
Once you have your shooting spot, turn the launch pad if able to get the rocket's pretty side, decal, name, etc., instead of just the dirty 1010 rail that your camera insists on focusing on instead of the rocket behind it that the rail is basically cutting in two.
Arrive early to give your lens and camera time to equalize to the temperature. Especially in the winter, but also in the summer. If you keep the AC in your house cold, the inside of the camera bag will be at that temp. Take the camera/lens out of the bag and set it on the seat while you're driving, and don't blast the AC directly on it. In winter, keep a couple zip-lock bags in your camera bag. When coming in from the cold outside, put the camera/lens in the ziplock while you're still outside, and seal with as little air inside as possible, then put in the camera bag. That will slow the temp stabilization from zero degrees up to 68 or whatever your house/car is at. It will also keep your camera/lens in the drier air as it warms, instead of the moister air in most warm locations. Most camera gear now has decent weather sealing but it's not a bad idea, especially if you're one of the guys who launches on a frozen lake in Alaska type of winter. North Carolina in November doesn't count.
Add a desiccant pouch if you have one.
When you're launching with your kids, know when to leave the camera at home, and just be with the kids. Snap a few iPhone pictures and be happy.