This is a form that I send home at the beginning of every school year.
Front: This is the side parents/guardians will fill out. It include the student's name, the parent/guardian's name, email, and phone number, the preferred method of contact, and a section for the parent/guardian to add any other information they deem necessary for you to know.
Back: The back is for you, the teacher. Once students return this form to school, you can file them away as your please. (I've found keeping them in a binder in ABC order is most helpful.) Then, whenever you need to contact a parent, you use the back side to document this information.
I've tried several different methods, and this is BY FAR, the EASIEST method I've used. I hope you find it as helpful as I do!