diaper bag

Depends on how long you will be gone, and how old your baby is. 
For every day, running around, usually about 8 diapers (you never know when you might get a blow out right after you change the baby). 2 changes of clothing. If you are bottle feeding, enough to make 2 bottles plus a bottle of water. If you are nursing, a cover if you want it, and nursing pads if you use them.
Blanket, burp cloths, wipes, hand sanitizer, tissues.
Wallet.
Phone.
Keys.  

Plastic bags (said blow outs), extra shirt for you. My son exploded on me once. Had to wear my jacket all day! Binky if the baby takes one. Snacks for you

 I have a daily routine when leaving the house with the diaper bag! You dont want to pack to much because then your bag will be exploding! If you feel like he needs 2 outfits then leave one in your trunk in a bookbag as well as an extra shirt for you. It could be smart to include some extra diapers in the emergency bag. But for your everyday journeys out my bag check is just the needed items. Such as, diapers, wipes, baby food, formula, bottle, and an extra outfit. Ive learned you dont need to pack water because 90% chance someone has a bottle of water you can buy or get a free cup of water! Or do what I did for a while. Put a case in your trunk! But you dont want to pack a sleepover in your bag because it will be heavy and in the way! :) 

I can't drive yet, I normally take the bus which excludes putting stuff in my trunk. And my diaper bag looks exactly like a sleep over bag!! Lol

Quoting OneLifeOneSon:

 I have a daily routine when leaving the house with the diaper bag! You dont want to pack to much because then your bag will be exploding! If you feel like he needs 2 outfits then leave one in your trunk in a bookbag as well as an extra shirt for you. It could be smart to include some extra diapers in the emergency bag. But for your everyday journeys out my bag check is just the needed items. Such as, diapers, wipes, baby food, formula, bottle, and an extra outfit. Ive learned you dont need to pack water because 90% chance someone has a bottle of water you can buy or get a free cup of water! Or do what I did for a while. Put a case in your trunk! But you dont want to pack a sleepover in your bag because it will be heavy and in the way! :) 

Geesh I always forget the keys!!!

Quoting Mommy2justone:

Depends on how long you will be gone, and how old your baby is. 
For every day, running around, usually about 8 diapers (you never know when you might get a blow out right after you change the baby). 2 changes of clothing. If you are bottle feeding, enough to make 2 bottles plus a bottle of water. If you are nursing, a cover if you want it, and nursing pads if you use them.
Blanket, burp cloths, wipes, hand sanitizer, tissues.
Wallet.
Phone.
Keys.  

I always kept an extra shirt in my car for this very reason. One day she threw up all over me. It was a summer shirt in the middle of winter. But hey, it was clean. 

Quoting JMama22:

Plastic bags (said blow outs), extra shirt for you. My son exploded on me once. Had to wear my jacket all day! Binky if the baby takes one. Snacks for you

I had a separate handbag with my ID and keys, wallet, etc, and then a diaperbag with the essentials for the baby, this way I didn't run into the problem of so much transfering of stuff from bag to bag.

Have you thought about getting a diaper bag bookbag?? They are handy when you dont have a car. My friend has one..and then she uses a purse for all her needs.

Would this be a backpack?  I hadn't thought of this.

Quoting OneLifeOneSon:

Have you thought about getting a diaper bag bookbag?? They are handy when you dont have a car. My friend has one..and then she uses a purse for all her needs.

its kinda like a backpack but its made like a diaperbag inside..