AZ Rifleman has some pointers.
He makes a lot of good points about how to treat non-gunnies that many of us regularly overlook. I have a few comments to add to his rules
First of all, here's my "taking a newbie to the range" document.
When I introduce a newbie to shooting, I make sure to do a safety and firearms function briefing before we even head to the range. At the range, I go over it again. After that, I try not to be overbearing.
When I go over the Four Rules, I usually add my own #5, which is, "If I say stop, or tap you on the shoulder, freeze. Take your finger off the trigger, but don't turn around or do anything else with the gun until I give you further instructions." There are a few reasons for this rule. Mainly, it is for safety. If you are correcting an unsafe action, you want to make sure they don't swing around with the firearm. This rule has saved many newbie thumbs, since they sometimes forget that the slide slams back on a semi-auto pistol, and put their weak-side thumb behind the hammer. Thankfully, I've always caught improper thumb placement in time to avoid a bloody situation. Note: for this rule to be effective, your newbie has to trust you. Make sure you ALWAYS act and speak in a safety-conscious manner.
The other reason I tell them to "freeze" is to correct technique. This is less common for the first trip to the range, because I tend not to spend more than a few moments discussing grip, stance, trigger control, sights, etc. However, one thing I find with newbies who are still afraid of their firearm is a tendency to lean way back, as if they are trying to keep as far away from the gun as possible.
There are psychological advantages for helping them overcome this fear quickly, and convincing them to "lean into" the shot. Aside from helping to absorb recoil, and improving accuracy, it gives them the feeling that they are really in control. Both women and men who shoot for the first time leave with a big grin on their face because of the sense of empowerment you get the first time you shoot. Nurturing that sensation will encourage them to do it again.
Regarding AZ's rule #9 for "At The Range", I find that range personnel can be among the worst. Even if you are at an otherwise empty range, the range officer can be a little over-zealous for a nervous newbie. This is why I prefer to give as much instruction as possible before we even get to the range. This way, they can walk in with some amount of knowledge and confidence which acts to deter that overly helpful resident-expert-on-everything range dude.
Once again, as AZ states, you need to cater to the needs of your individual newbie. Sometimes they will be extremely nervous and timid, and you need to take care not to overwhelm them. Other times they will be like sponges, wanting to soak up ever last little bit of information they can about this new exciting hobby.
There are times with others at the range can make a newbie's experience better. The first time I took my wife to shoot a handgun, she shot my .380 pistol. At the time, it was the only handgun I owned. The gentleman in the next lane over offered to let her shoot his 1911, and his .45ACP revolver. She happily accepted, shot some really tight groups, and has hated my .380 ever since (but loved bigger guns.) Having the option to try different guns is extremely important. Granted, you want to start with a low power gun, but don't assume that they will want to shoot it much after they see someone else at the range shooting a "real" gun.
Regarding #11, I've found that some people have a hard time "finding the dot" when using a red dot sight, especially on pistols. Due to the fact that it is hit-or-miss, and that I want to keep things simple, I don't even discuss sights before the first trip to the range, other than basic alignment to keep the newbie from shooting something they aren't supposed to. Generally, with a mostly proper grip and a low-recoil firearm, even if the newbie doesn't use the sights, they'll hit the paper at newbie distances. If they aren't hitting the paper, you have the target too far away.
AZ's #12 covers the two most important points. Have fun. Be safe. If your newbie isn't safe (or even if they don't feel safe) and/or if they don't have fun, then it was a wasted trip.