I'm an over packer. Always have been, just ask anyone whose ever gone on vacation with me =) That being said, I don't think you can ever be over prepared with babies. Under prepared yes, but not over prepared. I'm also crazy organized. Everything has its place, I have little containers and cubby holes for everything, and my diaper bag has 12 individual pockets (not including the main one) =) I love to be organized! =)
So here are my tips for making sure your diaper bag is well prepared. To prevent you bag from weighing 50 lbs, be sure to use small containers and travel sized products. Most baby products are offered in 2 sizes, one for home use and one for diaper bag use.
Pack only the diapers you need to "feel comfortable" my magic number is 7. I'm (very) uncomfortable leaving the house knowing that I have less than 7 diapers.
Take along a pair of jammies in case of accident. One footie sleeper takes less time and space than a full outfit (onsie, pants, socks, etc)
Small tube of zinc oxide diaper rash cream and a small tub of petroleum jelly will take care of any skin issues. (You don't ever need lotion)
Wipes, of course. I like the plastic bag style with the recloseable pop up lid.
A reusable changing mat. You can also buy disposable changing mats but that would get expensive.
One bib. Yes, just one. It has two sides, use them both! :-)
Nursing pads. Make sure you use the individually wrapped ones for sanitary reasons.
A couple of panty liners, just in case. And in a pinch, you can use a panty liner as a nursing pad! (Hey, don't laugh. I've done it!)
Lanolin oil or APNO cream for you nipples.
Tylenol for your aches and pains. Your vitamins and herbal supplements for your health and milk production. Use a pill container to carry just a couple days worth of pills at a time.
A receiving blanket. I've used a receiving blanket as a sun shield for baby's face, a towel for emergency sink baths (they happen!) a pillow, a toy, a teether, a burp rag, a nursing pad (don't ask LOL) and probably a hundred more things :-)
First aid and grooming kit. I have a handy little pouch that I carry all of T man's stuff in. Teething tablets, cold tablets, Tylenol, gas drops, nail clippers, hair brush, thermometer, nasal aspirator (I use the baby nasa kleen) cotton swabs and saline.
A roll of the disposable poop bags (arm and hammer I think) I use them more often for carrying home soiled clothes than I do for throwing away diapers.
Snacks if your baby is old enough and possibly a jar of food (don't forget the spoon) Bring a couple of sandwich bags to keep the food/spoon contained and clean.
Deodorant! :-) I leave the house at least twice a week without putting on deodorant LOL
Wallet, hairbrush, chapstick and Kleenex (for mom)
Toss in a few toys before your walk out the door and that's just about it. You'll find most products are good for multiple uses and you'll get very inventive with your on the go mom skills. I promise. =)