Moms who belong to the cool downtown mothers' group Bowery Babes have a rep for hosting the best playgroups in the City. With more than 800 members, the group is divided into "BB Generations," which are based on the babies' birthdays and led by a "Queen Bee." The original group, BB1—babies born in 2006—was founded by Melissa Errico. Then came BB2, then BB3 . . . now they are starting BB8. "The goal with playgroups is to foster real relationships and friendships," says Errico. Here, her tips on hosting successful group get-togethers.

Set up an RSVP system. Google Calendar is an option—you can invite everyone electronically, and moms can just email the hostess to RSVP.

Set a limit for attendees. Six-to-eight kids is a good range. The hostess then sends out an email to the entire group when the play date is full. You’ll find that some will cancel. There’s always a crisis with moms—a fever, an unexpected nap.

Set an end time. Put the start time and end time in the invitation so that you don't feel overwhelmed and wind up having to "kick out" your guests.

No shoes inside. It’s that simple.

No crumbly snacks. Ideal snacks include dried fruit, or those spongy Gerber wheels that don’t crumble. If babies have Cheerios or Goldfish, encourage snack-traps. If there are spills, just smile and let it slide. It’s a play date! Or, make sure you cover up what you don’t want to get ruined. I bought an alphabet mat ($19 at BabiesRUS) to protect my carpets from little accidents.

Spell out the rules upfront. In the email invite, you can cheerfully write: “I know this etiquette stuff is obvious, but the usual rules are . . . ” Sometimes it's good to cut-and-paste the rules from past play date invites. That makes it seem almost like an official document. The idea is not to sound like a bore, but to set ground rules to protect the hostess.

Keep strollers to a minimum. Request that moms "carry" babies or bring folding strollers. You can also buy a cheap plastic tarp at the hardware store to cover your entry floor or rug.  

Consider a theme. One time I hosted a classical music playgroup, and my father came and played piano for the kids. The BBs replicated it a few times by hiring music students to come with a violin or flute and play 20 minutes. Another fun theme is “Favorite Books,” where everyone brings theirs, and moms can volunteer to read aloud.

Go Potluck. We usually just improvise and don’t mind who brings what, but meals can be easily coordinated by listing things like six proteins, three fruits, two veggies and three sweets, and allowing moms to sign up. Or, ask people to bring things that can be easily shared. The main idea is to avoid the need for cutlery or plates and keep the hostess' cleanup to a minimum.

BYOB. All play dates should be "bring your own water or drink." This avoids a lot of mess and the host having to run around meeting drink orders.

Drop-off is not an option. Nannies cannot leave a kid, no way. Yes, two parents can come, and dads are always welcome.

No judging. Discipline is something no one can agree on, and methods vary. Moms all have different strengths and are learning things at their own pace. If a mom is stressed out and is abusive toward her kid, it might be a good opportunity to offer her ongoing affection and support.