What should be observed before beginning charting?

Before beginning charting, it is crucial to observe the patient's medical history. This information provides context about the patient’s overall health, any existing medical conditions, medications they may be taking, and previous dental treatments, all of which can significantly influence periodontal care and the approach to treatment. Understanding a patient's medical history helps in identifying potential contraindications for certain procedures, as well as assessing risk factors that may affect periodontal health.

The other choices, while important in the overall process of patient evaluation, do not directly precede charting. Brushing and flossing techniques are valuable for assessing the patient's home care habits, but they are not fundamental to the data collected in the initial charting process. Radiographs are important for diagnosis and treatment planning but are typically reviewed after patient history is established. Diagnostic casts can provide useful information about occlusion and tooth relationships, but they are not essential for the initial charting steps.