Something that I have found helpful when a parent does not use e-mail, or I don't have the time or telephone to call home is a notepad that keeps a carbon copy for me. This is not the exact type that I have found at my local teacher supply store, but it's similar.
It's nice to have a copy for your records, of course. But it's also helpful to let students know that if they "lose" the note, you will have them hand write another copy from the carbon version. I give students a couple of days to bring the note back signed before having them complete a second copy.
Now, you may also write letters of praise for your students. A note home does not have to be negative, and I would caution you from writing one that is 100% downright rotten news. You should lead in with a sincere compliment. If you don't have even a small praise for the child, I recommend holding off on that note until you can think of one. (A compliment also increases the chance that the child will show the note to the parent in a timely manner.) Also, what are you asking for the child's parents to do for you and their child? Be specific and realistic.
Here's a sample:
Dear Smith Family,
Tracy is such a bright child; I always look forward to reading her papers and getting her point of view after we read a story in class. Lately I've had trouble with her speaking out of turn during class discussions. I've spoken with her about the importance of giving others time to voice their opinions and waiting for me to call on her join in the conversation. Will you please talk with her about respecting her classmates' contributions to our group discussions? I sincerely appreciate your support at home.
Similar advice goes for e-mails sent home with regards to content. Something kind + the issue at hand + what the parent can do to help + thanks for your support = a reasonable request.
Even if the child is doing handstands on your last nerve all day long, you'll get better results when you let parents know that you are all on the same team whether you contact them in person, over the phone, or in writing.