Always have a cache of bottled fresh water in your home and vehicle. Seriously, you can only go 3 days at most without water, and if you lose your water source in your home you need water to drink and cook/bathe with. If you are at home and know you’re going to lose water for a long time, don’t know when it will come back, and SHTF, fill up your bathtubs and sinks with water. Boil and drink that before cracking open your bottled water supplies.
Also it’s a good idea to put a first aid kit in your car, as well as a couple wool blankets, an extra jack, extra set of long jumper cables, extra tire nuts, an extra tire nut screw, and some road flares. Car accidents are common and these items can prove invaluable.
Another thing is to have a small bag with specific gear near you at all times. A leatherman multitool, flint and steel, knife sharpener, gauze pads, duct tape, hand sanitizer, iodine tablets, reusable water bottle or canteen, sunglasses, bandanna, dryer lint, headlamp AND small flashlight with extra batteries, orienteering compass, lots of extra currency, and fishing line+hooks are all small items that prove useful if you need to survive any period of time. Pack the ones you can (no knives for you highschool/airplane passenger/British anons) and keep em in a small but tough bag in your work desk, car, etc. so that if you had to evacuate suddenly you could grab that bag and leave quickly.
In addition to that small “bug-out-bag” you should prepare a hiking backpack with more long term big-out gear. Lots of guides detail how to build a long term innawoods kit, but this one won’t be as easy to get as you probably won’t end up bringing it with you or leaving it in your car. It’s for if you had to bug out and had time to get home and prepare.
Hunting rifles or shotguns chambered in common rounds are the best firearm, followed by a rifle that is flexible, reliable, and accurate. Some handguns are good for small game also, but lack range.