Before applying a new font to existing text, what is the first step?

The first step before applying a new font to existing text is to select the text you want to change. This action is essential because changing the font will only affect the text that is currently highlighted or selected. If no text is selected, your changes will not be applied to anything, rendering the action ineffective.

Highlighting the entire document would alter all text at once, but that may not be the desired action. Opening the Font dialog box is necessary for making formatting choices, but it comes after selecting the text. Saving the document is generally a good practice but is not directly related to the process of changing the font itself. Therefore, selecting the specific text you wish to change is indeed the correct initial step in the process.