Why you need her: She gets you through your "I don't know what I'm supposed to do next" moments. For Jen Matlack of Bethel, CT, mom of 3-year-old Mae, this friend is Janet, whose kids are 22 and 20. "If I have any concerns -- Mae not napping, Mae constipated, Mae not having playdates, or maybe my own parenting worries -- I always check in with Janet. She has offered me a lot of reassuring guidance," says Matlack. "And even though she's my older, wiser parenting friend, she's also a kid at heart, just like me, so when I'm around her, I get the best of both worlds: wisdom but also a wild side."

How to keep her: The good news is that she probably loves giving advice as much as you love getting it. "Motherhood can seem like a thankless job, so it's great to be recognized and be able to share what you've learned," says Kovarick. If you've asked for help, try to remember to call and tell her how well her ideas worked out. And even though you may not know yet what it's like to be in her shoes, you can still be a sounding board for her older-kid problems.

The I'll-Do-Anything-For-You Buddy

Why you need her: She'll help you with your garage sale, drive the kids to soccer, and bring over lasagna when you're dealing with a crisis. For Erin Hart of Arlington, VA, her husband's best gal pal, Laurie, is this friend. "When I was pregnant with my second child, we were in the process of redoing our closets, and my baby girl arrived a week early. Let's just say the bag I brought to the hospital was a grocery bag, with a nursing bra, underwear, a toothbrush, and a hairbrush. There wasn't much time." The day after Erin's daughter Emerson was born, Laurie called a sitter to watch her own two boys, came over, and washed, folded, and organized all the baby's clothes. "It was incredible," says Hart. "She basically dropped everything to come to our rescue. And the first week we were home, she brought over a fully cooked meal. I'll never forget that."

How to keep her: Friendships don't come with vows, like marriages do, says Marla Paul, author of The Friendship Crisis. It helps to remind your friends that you care. "So many friendships fall apart because one friend feels neglected," says Paul. So return the favor. Maybe you don't have the time to drop everything, as she always seems to, but make an effort. When she's going through a tough time (or even having a tough week), instead of cooking the family a homemade meal, as she might, drop off a pizza or a gift certificate for her favorite Chinese takeout.

The Slightly Glam Girlfriend

Why you need her: For inspiration (it is possible to be a fashionable mom), advice (how does she get out the door looking so great?), and a wardrobe you can borrow. My friend Mary fits neatly (of course) into this slot for me. Every photo she e-mails me of her and her daughter shows the two of them looking gorgeous, whether in their matching bikinis or out to dinner at a fancy restaurant I couldn't imagine going to with a kid.

How to keep her: You admire your friend's got-it-togetherness, so tell her, says Kovarick. She surely works hard at it and will appreciate the compliment. Watch out for your own jealousy or embarrassment, though. Most of us feel that way sometimes, but if she's a real friend, she's not trying to make you feel bad about your relative lack of style or organization. She likes you for you -- though if you're still wearing mom jeans, maybe she can help you trade up.

The Brutally Honest Pal

Why you need her: We all need to hear the truth sometimes. It can sting, true, even if you asked for your friend's opinion. But if she cares enough to tell you not just what you want to hear, then she's a keeper. For many women, sisters play this role; for others, it's a longtime friend, or a particularly outspoken newer one. The trick is distinguishing between someone who's just bossy and someone who actually puts thought about you into her opinions. You'll know the difference (one clue: If she only ever criticizes your choices, she's not helping).

How to keep her: It may take a day or two for you to digest what she's told you, but once you have done so, call your friend and thank her for being honest -- even if you don't agree, says Kovarick. We don't have to be exactly like our friends -- Twitter would be seriously boring if we were -- as long as we look out for each other, even while we're looking out for our kids.

Patricia Curtis, a writer in New Jersey, often sips coffee with friends while her 1-year-old gnaws on her purse.