A new family group record should be used for each couple on your pedigree chart. You may also use a new family group record for additional marriages. For example, if your grandfather married again after the death of your grandmother another family group record would be used.
A family group record will also contain a place to list the preparer of the family group record and contact information. This allow someone who is interested in your family group record to contact you.
There are two additional pieces of information that are part of the family group record, they are notes and sources. I use the notes section for biographical information and research notes to myself. The sources section is probably the most important section of this whole form. In this space you will include specific information about how you know each fact on the form to be true.