I once knew a woman who was so reputed for having so much stuff in her purse that she tossed in a Barbie kitchen sink, just to say that she really did carry everything and the kitchen sink. Some days, I feel like I should do the same for my range bag, except maybe something a little bigger because sometimes, you really need to scrub under your nails. While you don't need to (and probably shouldn't) go overboard, there are a several things you should pack when you go to the range that shouldn't be skipped:
Range nutrition and hydration has become an increasingly important part of my routine over the past year. Before, I found it easy to forget that a day spent shooting was a day spent outside and exercising, with all that implies. I often wondered why I got cranky and my performance suffered by the time I got to the last stage in a match until someone reminded me that I hadn't eaten anything since my crack-of-dawn breakfast and it was now well past noon. The easiest fix for me was to keep some protein bars in my bag, or to remember to pack a full lunch if I knew I'd be pulling pit duty. Making sure to eat a complete breakfast is also helpful - a sugary donut isn't enough. I've seen people snack on everything from fruit and nuts to fancy sport goos, so it's worth experimenting to find what works to keep your head focused and body running. In addition to, and often more important than, food is hydration. Liquids are obviously vital when temperatures run high but often forgotten when the weather starts to turn cooler. While you might not need the liter of water per hour I've gone through mid-summer, it's possible to get dangerously dehydrated even in the middle of winter. You may also find, as I did, that staying on top of your fluid intake will help increase your performance since dehydration can show up with symptoms like weakness and confusion. I like plain water in a hydration pack that is part of my range bag to reduce the number of things I'm carrying around, and have started adding electrolyte tabs (in about twice the amount of water as recommended) for longer days on the range. My shooting partner lives on low/no-calorie sports drinks.
Range safety includes personal protective gear, but doesn't stop at just your regular eye protection and ear muffs/plugs. I always keep spare lenses or an extra set of eye pro around in case lighting conditions change or if my regular pair breaks. Extra plugs live in my bag for similar reasons; muffs can get uncomfortable in hot weather conditions or on a long day, and I've had earplugs fail completely while taking them in and out during breaks. They're also small and cheap enough that I can give them out to guests or shooters who need extra hearing protection without wasting a lot of room in my bag. Beyond that, I also stash sunscreen and work gloves in side pockets. Sunscreen isn't only for protecting yourself from burns - including during winter - it can also be an element of protecting yourself from heat exhaustion and its big brother, heat stroke. Work gloves don't take up a lot of room and can prevent a lot of scrapes and splinters when helping set up or break down a match. Even, and sometimes especially, the "light" tasks like painting steel, collecting targets for the dumpster, or corralling the stakes used to hold down temporary walls can benefit from having a sturdy set of gloves. I picked a pair that fit well enough that I also can shoot in them in a pinch if I've been surprised by the cold. One final thing that's important and that I'm working on being better at bringing to the range with me: waterless hand cleaners. In addition to lowering lead exposure, wet wipes (whether of the deleading variety or not) can be refreshing on a hot day and a heavy duty gel/cream cleaner can be more effective than regular alcohol-free sanitizers when you've gotten especially grimy during set-up/re-set/tear-down (sticky paint on steel targets, I'm looking at you!).
You'll notice I haven't mentioned things like pens/markers, notepads, shot timers, mag loaders, knives, tools, spare parts, membership cards, and the litany of other things that crowd range bags. To me, most of those are relatively obvious or are things I can live without for one trip to the range (except when I forget the right magazines to go with the guns I actually brought with me...), but the items I've concentrated on in this post are a necessary part of my kit every time I head out to a match or class or even just a day of plinking.