I have a confession. The Rowhouse Livin' household does not maintain a bug-out bag.
Wait, first: what's a bug-out bag? Also called a 72-hour survival kit, a GOOD ("get out of Dodge") bag, a ten essentials bag, or a personal emergency relocation kit, it's a pre-packed backpack, holding everything one person would need to survive for three days, and available at a moment's notice for an emergency evacuation. The bag includes food, water, first-aid supplies and daily medicines, hygienic supplies, basic camping items, paperwork (identity documents, medical records), and cash. That's not anywhere near a complete list, but you get the idea.
There are a million websites selling pre-filled bug-out bags, and a million other websites telling you how to pack your own. In the end, as with anything else regarding emergency preparedness, you have to look at your own situation and figure out a solution that works for your household. When it comes to evacuations, the first question to ask is:
Why would I ever be ordered to evacuate?
The more paranoid survivalist websites and discussion forums fear civil unrest. I won't go so far as to call that kind of fear laughable, because riots do happen. But they're infrequent, they usually don't last longer than a day, and to some degree they're predictable, sadly -- sports team victories, or excesses on college campuses. But in the U.S., even multi-day demonstrations that degenerate into chaotic situations, or week-long riots leading to curfews and a mayor calling in the National Guard don't tend to lead to government-ordered evacuations. (Of course, you may want to leave anyway.)
Authorities order mandatory evacuations when there are natural disasters on the way: flood, wildfire, volcanic eruption. Or not-so-natural disasters, like chemical spills. Do you live close to a river delta or freight train tracks? Then you should probably have a bug-out bag ready to go!
So what's in the Rowhouse Livin' bug-out bag? We don't have one, as I've said. We're not in a volcano zone. Our home is not near freight train tracks or the interstate highways. I don't live on waterfront property. The buildings on either side of mine are well maintained, placing us at a very low risk of being affected by a building collapse. Probably my biggest risk is a water main failure, though to be honest I'm not too worried about that, either (because our building is on a slab, without a basement). Call me an optimist prepper, but I honestly don't think I'll get an evacuation order on my block any time soon, because I think my risk of those events that trigger mandatory evacuations is vanishingly small. So I don't keep a full bug-out bag at the ready. Rather, I keep an envelope with our important documents in a convenient location by the front door. And by "important documents," I mean our passports, our birth certificates, our Social Security cards, my homeowners insurance policy, a map and a planned route on foot out of the city, some addresses and phone numbers, and a small amount of cash (think: what if the banks are closed, or ATMs aren't working? But also: realistically, how long would it be before I can use an ATM again?).
Everything in moderation, even emergency preparedness. One should be prepared for emergencies, but one shouldn't go overboard. Seriously consider the risks that you face in your area, and plan accordingly -- and reasonably.