Making your own lets you adjust its contents to your climate, budget and situations. I hope people will take the kit I've put together as a base to start their own.
Lets get started...
Step 1: Assembling the contents
1.) Jumper cables (aka booster cables)
2.) Multi-Tool (one of those pliers that have tons of tools in the handle)
3.) Map (local area or area you'll be traveling)
4.) First-aid kit
7.) Duct tape (because you can fix a lot of things with Duct tape)
8.) Rain coat (the folded $1 type)
9.) Emergency blanket (the folded $1 type)
10.) Folding shovel (entrenching tool)
11.) Fuses for fuse box
12.) Water bottles
13.) Protein bars or M.R.E. (meal-ready-to-eat)
14.) Reflective tape or reflective triangles (flares are hard to find)
15.) Old Cell phone, fully charged. Call customer service via the phone to make sure it works. Do not make test calls to 911 (Service is not needed to make 911 calls). Most modern cell phones and cell networks can triangulate your position, this is very handy in an emergency.
16.) Lighter or water proof matches, or flint rod.
18.) 550 cord (named after its tensile strength) or para cord. Google the number of uses for this stuff, you'll be amazed.
I'll address some of these items in the next few steps.
Step 2: Fire Is Important
A fire will give you warmth when it's cold, chilly, and downright freezing outside.
A fire will provide you light during darkness so you can see to do other things.
A fire will allow you to cook your meals and boil water so you can consume them safely.
A fire will dry out your clothes when they've become wet so you won't get sick.
A fire will provide a way to signal for help, both, during darkness and daylight hours.
A fire will protect you from wild critters, they don't like fire.
So in short, add fire making devices to your comfort level.
Step 3: Organize The Kit
In my case the jumper cables are large and would be cumbersome to move out of the way if I neede to get to the first-aid kit, so they'll go on the bottom.
Step 4: Communication Can Save A Life
Don't have an extra phone? Grab a $20 pre-paid phone(w/ roaming), because $20 is cheap insurance.
Step 6: Make It Easy To See
This is the same type of reflective material you see in traffic signs, this stuff really pops when you shine a light on it at night. This add-on will be great if your changing your tire in the dark.
Remember you can add and subtract anything you want from this basic kit, just make it work for you and your climate. For instance I added a shovel because I drive in the snow parts of the year. If I lived in Arizona I might add a gallon of water to this kit, you get the idea.
Hope you have fun making your emergency kit.