Here are some more ideas based on 36 trips up Whitney.
1. If you are solo, and if it is your first trip to high altitude, and if you are just a tiny bit uncertain about navigation, then it is not a stupid idea to team up with others at the trailhead. The problem is that there will be very few hikers going at this season. However, there will be a few. The trick is in finding them. So, consider picking the early hour that you intend to begin, like 3 a.m. or whatever, and then arriving at the trailhead 30-60 minutes early to get your car parked and your boots laced up. Then just kind of hang around until you see another group starting. If you start walking just five minutes behind them, that is good. You will see their headlamps in front of you, and it just gives you a target to keep moving toward. If they seem like trustworthy hikers, then you might accidentally join their group. However, a few groups will be tragically slow, and you have to know when to cut your losses and move out on your own.
2. You will probably be carrying a tiny first aid kit. Typically a first-timer needs to take one or two aspirin tablets when they get up around 13,000 feet, and it helps to have those wrapped up in a bit of plastic and stuck in a very handy pocket. It really slows a hiker down to have to stop and go through everything in a pack to find one small item. Additionally you will probably have a small ball of first-aid tape or maybe an Ace wrap for an ankle. But you know what your potential medical weaknesses are.
3. I mention aspirin because many first-timers are a little off-base on their water consumption. As a result, they get dehydrated, and then a headache sets it. That takes a few hours to develop, and that's why it happens around 13,000 feet. Sometimes it is because of modesty. There are no trees or bushes by the time you get to 11,000 feet, and sometimes you have to look hard to find a place to relieve yourself. That causes some hikers to fail to drink enough water in the first place.
4. Some first-timers get too wrapped up in the concept of spending a night out on the trail up high on the mountain. Well, yes, it happens, but it is rare. Instead of loading yourself down with all manner of gear to meet that possibility, I suggest going a tiny bit slower and then thinking about what you are doing more. The problem is that some hikers get up to 13,000 feet and they get punchy from the thin air... and then they start making bad decisions. For example, they stop for a minute, take a photo, drink some water, and then continue. About 15 minutes later they realize that they have lost their camera or their water bottle. It is better to strive for a consistent moderate pace.
5. Water management is generally an issue. First-timers never know how much water to carry from the start. Since this is October and this is well past the prime season, I can't say too much. You may be dealing with water freezing. However, many hikers will start with about two quarts of water, and they sip on that sparingly all the way up. By the summit, they are on the bottom half of the second bottle. So, you can pick up some more raw water on the way down and treat it. Where it the raw water? I don't know for this season. During prime season, it is generally in two places around switchback #25. However, in this season I don't know what is frozen and what is still flowing. If you know that you drink a lot of water, then increase this to three quarts to start with. I've done the entire uphill stretch of trail on as little as 8 ounces of fluid before (Gatorade), but I don't recommend that for others.
6. I'm not a big fan of hydration packs. You get one leak, and then you are in trouble. Traditional water bottles are a little more foolproof unless the water freezes. If so, stick the frozen bottle under your jacket while you are moving, and it will thaw out in no time.
7. Despite how cool it might be up there, one of your big concerns should be sunburn. For cool weather, it is easier to cover up for sun protection rather than gooping up with sunscreen. One or two bandanas ought to do it.