There was a short period of time after baby No. 2 when I transitioned from a stuffed-to-the-gills diaper bag to an actual purse. A normal purse-one that didn't weigh 10 pounds or contain crushed cereal, sippy cups and baby wipes. But now with baby No. 3 in tow, I'm back in full-on diaper bag mode, and have the strap indents on my shoulder to show for it.

Luckily, diaper bag fashion has come a long way in the past few years, with even top designers offering their own trendy bags for baby stuff. My first bag nine years ago-a big, boxy, black tote-screamed diaper bag. But bags these days are so fashionable it's almost impossible to tell their main purpose is to lug around diapers and butt paste.

Fashion aside, the diaper bag is your constant companion, and when packed correctly, contains everything you need for a whole day out with baby. A well-designed diaper bag is a godsend, so here are few things to look for when shopping for that perfect bag:

- Make sure it's a style that you like. Seems obvious, but you're going to be carrying this bag for two years, at least. If you love one that's a little pricey, consider the length of time you'll be using it, day-in and day-out, and you might realize that it's worth the extra investment.

- Is it functional? Sure, the thin straps look pretty, but what happens when you are trying to carry your baby and groceries, while pushing a stroller? You'll be cursing those thin straps. You want a style that has different strap options, and ideally ones that you can attach to your stroller's handlebars.

- Size matters. Even my biggest diaper bag sometimes doesn't feel big enough. Make sure to find a bag that is roomy and has plenty of pockets. It's no fun digging around for a diaper at the bottom of your bag when you're holding down a squirmy baby.

- Can it be cleaned easily? Babies are messy, no doubt about it. Having a diaper bag with a wipeable surface is a good way to go. Coming from a mom who had grape juice spilled all over her gorgeous canvas diaper bag ... yeah, wipeable is good.

- Is it something your partner would carry? If you want to buy just one bag that both of you will use, consider a more neutral design that any caregiver would be comfortable carrying around. Save the bright florals for another time.

Now that you have an idea of what kind of diaper bag to choose, what about what to put inside? Aside from the givens such as diapers and wipes, here are some of the most important things in my bag:

- Change of clothes: Having an extra set (or two) of clothes for the baby is essential when you're out and about. If you've ever experienced a diaper blowout and not had that spare onesie, you know what I'm talking about.

- Plastic bags: Having a few plastic bags are huge for when you need to dispose of a dirty diaper, or need to stash dirty clothes. For added convenience, great little plastic bag dispensers are available that you can just clip inside your bag.

- Nursing cover: This is something else you don't want to find yourself without. Having a makeshift cover such as a burp cloth or your kid's sweatshirt (ahem) sometimes can make nursing in public even more awkward than it can be in those first few months. And if you're not nursing, a nursing cover can offer a quiet place for babies who are bottle-feeding or sleeping.

- Snacks! Not for baby, but for you. In those early months of sleep deprivation, staying nourished is really important for keeping your energy up. Pack a few granola bars, almonds or whatever is healthful and convenient. That infant carrier can feel very heavy after a few errands.

- Hand sanitizer: I prefer hand sanitizing wipes, which I feel clean my hands better than gel when there is no sink in sight. If you're preparing bottles or giving your baby a finger to suck on, you want to make sure your hands are germ-free.

There's a lot to stuff into that bag, but with the right bag and the right stuff, you'll be good to go.

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