Today, it's all about BOB. A bug out bag, by any other name is a bag. It can be anything you want it to be. It can be a simple backpack costing just $20 all the way to an elaborate system costing more than $250. Either way, it will perform one basic function: gear storage.
What kind of bag you decide to use will depend on your situation and what you intend to use it for. If you are an urban dweller, and only need something to get a few miles, you could probably get away with a lot less than the guy who might have to walk a few days to get home. For the purposes of this post, I'm going to focus on the guy who needs more gear. You may or may not need all of this, but it will cover nearly everything.
The setting: You travel more than 50 miles away from home everyday. You live in an area that is at higher risk for earthquakes and volcanoes than some places. You have a lot of bridges between you and your house, and traffic ranks in the top 5 worst in the nation. You're going to need a bag, but you can't just have any bag. You need something that will have a few extras that your high school Jansport backpack didn't.
Requirements for a Bug Out Bag:
1. Durable! Durability needs will vary per user, but try to buy the most durable bag you can afford. Military style bags will probably get you the most bang for your buck because they use simple materials and are built for combat.
2. Roomy. Get something that will have enough room for your 72 hour kit.
3. Comfortable. This is where bags can get very expensive, so be careful. You will need something that has a good suspension system. Padded shoulder straps, sternum straps, and a good hip belt are a must. Get a padded hip belt to make your life better. Having rigidity in the pack helps distribute load between the shoulders and hips.
4. Low profile. Don't get an outrageous "LOOK AT ME" pack. I have one of those for camping and backpacking. It has Osprey embroidered proudly across the back so everyone following me can see it. That pack was expensive, it's rugged, and it's not for survival. Get something that gives you a lower profile.
5. External Attachment points. More of a "would like to have" item, external attachment points on your pack will allow you to bring along things that may not fit inside, like a sleeping bag or tent.
Now, if you know that you will never be more than a day's walk from home, you probably won't need anything more than a basic backpacking pack, and that's okay. You can buy them used all over the place and they are in really good condition. I would avoid external frame packs because, even though they can be comfortable, they are cumbersome and take up a lot of space in the trunk of your car.
The particular pack I have my eyes on has all the required things for my 50+ mile from home activities and none of the fancy crap that would make me stand out. It is the BUGOUT GEAR Tac Ruc E&E bag.
I chose this design based on all the 5 requirements that I wrote above. It has a nice comfy suspension system, it's large (5900 cu in), it has attachment points all over it, it is hydration bladder compatible (3 liters), it is made of rugged canvas, and to anyone seeing me with it, it looks like a humdrum army surplus bag. But this is a lot more.
Now, I'm not suggesting you go out and buy THIS particular pack. This is simply what I'm looking at for my uses. This pack comes in a tan, camo, and black. For emergency use, the tan one might work the best simply because it will blend in to the surrounding environment. Camoflauge will as well, but in an urban setting, camo will actually attract attention. Black isn't found in nature much, so even at night, it could stand out.
Do some research. Check out uscav.com, or just google bug out bag and see what you get. Visit an army surplus store, or a backpacking store. Don't be disappointed if a bag you thought you liked doesn't work out in the end. It is going to take some research and footwork on your end, but when you find what works for you, then your hardwork has paid off.