Definitely, call any parent even if you're looking them up in the phone book. Or, depending how old your child is, ask his/her friend to write down the home phone number.
Last year, a phone # was wrong in the directory, so I sent a note to school marked in an envelope with the child's name. In the note, I wrote that my DS would like to have a playdate with their DS, and I'm writing this note because I didn't have a phone # how to contact them. I included my #, and then I left it up to her to call me. She called, our kids had a great time on their playdate, and all was good! Actually, she was appreciative of my call.
I ask my son who he wants a playdate with and then I pick up the directory and call out of the blue. It is hit and miss. What works best is to build a rapport on the sidelines of a sports field and then ask. Hint: don't tell your child that you are doing this. Often the answer is no, and it's just easier if your child doesn't even know the conversation took place.I have my children first ask the child they'd like to play with if they want to come over and play. If they say yes, then yes I do call the parent and say my daughter so and so is in your daughters class. She'd love to have her come over and play after school (or whatever) if she's interested. The other good way is to have a little party (maybe for Halloween) and invite say all the kids in the class or all the boys. You can look up their addresses or call them and have the group over for starters. This way you can meet a few kids and a few parents, then keep it going from there. You could just call it a meet and greet fall party now that school has settled if you didn twant toget into the whole Halloween deal. Make it short and sweet, say after school some day for an hour and a half or so. If you do the party, you really cant send invites to school unless you are inviting the whole class.This is going to sound like a strange question, but how does one go about setting up playdates? My son doesn't go to the school that we are zoned to, so we don't really know the other kids in the neighborhood all that well (I work in the district and selected a school closer to where I work).