There are many names for a Go Bag, depending on its desired function. Personal survival kit,  Get home bag, 72 hour bag,  Get out of Dodge Bag, World is about to end bag.  You get the idea.  Also depending on where you keep your bag and if you have to carry your bag for any length of time or distance will also determine how much you will have in your bag.  
I recommend the following bags, and each will have similar items yet be unique due to its size and storage space.  A bag you keep at home, a car bag, and a work bag.  

 Why do you need a Go Bag at work? I will list a few times that myself; friends and family have used their work Go Bags.  Snowed in at work, earth quake, tornado, hurricane, active shooter, police and terrorist activity, roads shut down.  The list could go on and on.  In our modern lives we spend most of our time at work, or getting to work. This is why I think you should start with a Go Bag for work. A car bag is also vital and much larger, but that is outside the scope of this article.  

 I want to cover what to have in your Go Bag that is practical, and one that you will actually carry with you.  If it is to big, or cumbersome you won't carry it and it will do no good if you leave it at home or in the car.  
The bare minimalistic view of a survival kit/Go Bag is a sharp knife, a metal cup, and a spark/fire producing device.  On the other end of the spectrum is a full 75 pound ruck sack that has everything you will need for 3-14 days,   (including the kitchen sink).  

 You should make your own additions and subtractions from this list.  This is your life so make your Go Bag for you. We all have different needs, jobs, environments that we work in.  We all travel to different locations and different distances to work.  We all have different comfort levels.  All of this should be considered when making your Go Bag.  There is no wrong way to make your Go Bag, except not having one.  

 I will cover what I consider a practical Go Bag that is easily carried on your person in a small backpack.  It will cover you for about 24 hours and with some small additions up to 2 days in an emergency.

 Every Go Bag I recommend starting with a First Aid Kit.  In my experience it is always better to start from the top down on your first aid kit, that way if something has to be left behind for whatever reason, you have the lifesaving items at all times.  Please relies none of the following supplies will do any good if you don't know how to use them.  Get trained and take a course in First Aid/First Responder.  

Time to death in emergency situations:
Severe bleeding- death in less than one minute
Anaphylactic shock- death in 1-5 minutes
No oxygen to the brain- death in 5 min
No water -death in 3-5 days
No food- death in 5 to 8 weeks.

 Now Let's pack according to those numbers.
First do you have severe allergies to bee stings, any foods such as peanuts, shellfish, or eggs?  If you do, pack an epinephrine pen!

 I start with one commercial tourniquet, and a set of tourniquet material to make a second one.  The material is as simple as a bandana and a small solid 4-6 inch stick.   This is for extremity bleeding that cannot be controlled with direct pressure or a pressure bandage.   The experts in the field also use the tourniquet for any serious extremity bleeding under fire.  

 One pack of commercial blood clotting material, pack enough for at least one wound.   These items stop bleeding on contact when direct pressure doesn't work.  

 Occlusive dressing for puncture wounds of the upper torso.  

 One roll of Kerlix Gauze Bandage Rolls 6-Ply, Sterile, 4.5" wide x 4.1 yards
One Ace wrap 4-6 inch
Approximately 4-5 feet of Duct Tape, this will fit on any small cylinder.
The above covers all bleeding that would be life threatening and this will all fit in something the size of a coffee can.  I have even fit all of this in my cargo pockets.  In my opinion the above items are in the category of Have to Have!  

 Next are the nice to haves.   
*    First aid instruction booklet
*    2 Adult doses of Benadryl (for allergic reactions)  
*    2 packets of aspirin (81 mg each)
*    1 breathing barrier (with one-way valve)
*    Eye wash solution
*    4 butterfly bandages
*    1-2 triangular bandages
*    1 adhesive cloth tape (10 yards x 1 inch)
*    2 absorbent compress dressings (5 x 9 inches)
*    5-10 adhesive bandages (assorted sizes)
*    2 pair of nonlatex gloves (size: large)
*    1 roller bandage (4 inches wide)
*    5 sterile gauze pads (4 x 4 inches)
*    Scissors
*    Tweezers
*    2 antibiotic ointment packets (approximately 1 gram)
*    2 antiseptic wipe packets
*    2 hydrocortisone ointment packets (approximately 1 gram each)
*    1 instant cold compress
*    moleskin,
*    insect repellant,
*    sunscreen

 Now that the first aid kit is packed, we will start on the survival item for a 1-2 day stint out and about.  
Water- carry one liter along with water purification tablets, and I suggest a water filtering devise.  They are fairly inexpensive and lightweight.  Water can be very heavy to carry, approximately 8 pounds per gallon, so having a few ways to make water safe to drink is very important.  

 Food-for this bag I recommend keeping it simple.  Use protein bars; pack enough for 3-6 meals depending on how long you want to pack for.  I use emergency food bars similar to ones used on lifeboats.  Each small pack is enough food for one person for 3 days.  Shelf life is 5 years and they are packed to withstand the extremes of natural disasters.   
Lighting- I recommend a headlamp type of flashlight, it keeps your hands free, and always pack an extra battery and bulb.  Under the lighting category glow sticks come in very handy and are cheap, lightweight, and can be used for times you don't want to use your flashlight, thus saving the battery and your light.  
Fire- I start with a couple disposable lighters, one pack of waterproof matches and a medium sized candle.

 You also should carry (in a Ziploc bag) some fire starting tinder.  I carry WetFire fire starter, but you can soak cotton balls in petroleum jelly and carry a few of these in your Ziploc bag. (Also duct tape and hand sanitizer make good fire starters)

 Poncho- I use a heavy weight style with grommets in the corners. The reason I choose this style is so I can use it as a shelter if necessary.  Being wet is a moral killer and can literally kill you.  Experts report that hypothermia is the number one killer when exposed to the elements. When you are wet, hypothermia can set in at temperatures as high as 70 degrees.  Don't get wet!

 2 Large commercial garbage bags- these have a multitude of uses.  Such as a Poncho, shelter, ground cover, waterproof gear, water gathering and transporting, portable shower/bath.  Just to name a few.

 Solar/emergency blanket-they are cheap lightweight and will be used as a sleeping bag/blanket.  
2 Bandanas- Yet another lightweight cheap multi use item.  I believe I have seen as many as 50 uses for a bandana on some survival web sites.  Don't leave home without one!

 A quality multi-tool- this tool should be QUALITY.  You don't want to use it once and have it break and or injure yourself.  It should have a solid knife blade, a saw blade, pliers, flat head and Philips head screw drivers, and wire cutters.

 
Duct tape- among all of its uses it is also a good fire starter.   

 Map of your aria- you may need to take unfamiliar routes off the main roads to get to safety.  Always water proof your map.  This can be as simple as keeping it in a Ziploc bag.  

 Compass-if you are off road or in unfamiliar territory this can be invaluable.  Learn basic compass and map skills.

 Money- carry as much as you are comfortable with in small denominations.  Cash always works.   
550 cord-like duct tape, para cord has many practical uses, its light, cheap, and carries very easily.
Pencil and notebook - for recording information or leaving notes.
Mirror-the uses include signaling, and observing around corners without exposing yourself.
Whistle-you will lose your voice yelling for help for very long, also a whistle can be heard in extreme conditions where the human voice is drown out very easily.

 Hygiene kit- include items such as a toothbrush and tooth paste, dental floss, bandana,  a pack of wet napkins/baby wipes, and hand sanitizer (hand sanitizer is also a fire starter).
Leather work gloves-keep your hands safe.
Socks- it unbelievable what changing your socks and brushing your teeth can do for your moral and comfort. Always take care of your feet and teeth in any extended survival situation.  Also if you have ever done any hiking, a fresh set of socks can prevent you from getting blisters.
Walking shoes- if you work in business/dress shoes you may want to pack some comfy practical shoes you can walk/run in.  Keep in mind; they do take up some space.

 Pants-again if you work in business/dress attire, you may want to pack some practical hiking pants, maybe even water proof.   Avoid jeans!
A change of clothes and a pair of leather gloves allows you to change out of your business/dress attire and into something that offers more a more practical survival wardrobe.
Face Mask- N95 Face Mask is what the experts recommend.  If there is dust and debris, this can be a life saver.    
Cell phone charger- to stay in contact and check the news for updates on weather and the emergency situation.  
Self Defense Items-use your judgment, however all of us should carry some type of X Weapon.
So are you going to be a Go or a NO GO in an emergency situation?  Carrying your Go Bag does not guarantee anything.... However you will be prepared for 80-90% of emergency situations to protect youself and get home to your family.