Numerous tragedies or dicey rescues could be avoided if day hikers simply wore a belt pack containing a waterproof poncho or parka and a warm dry sweater, even on seemingly mild days. In dry areas, carry extra water. Memorize landmarks. I'm pretty well equipped for just about anything, since a big pack is involved if LF gear is being carried anyway. Don't put all your eggs in one basket : in other words, when entering a remote area, have a suitable paper map and not just a GPS or phone - those might disappoint you. And never underestimate the importance of sufficient footwear. I've encountered macho young runners way back on mtn trails where a simple twist of the ankle didn't allow them to keep up their body heat, a storm suddenly moved in, and they'd probably be dead if I hadn't come along with a spare coat in my pack. There are other simple life-saving rules, like get over any high passes or bare patches before lightning sets in. If the trees all around you show a history of lightning scars, that's not a good place to be. It's far easier to slip and drown in a stream than unexperienced people think. A bison herd isn't a petting zoo, because a bull is a bull. Headlamps are valuable, as are spare batteries.