As you get more comfortable in InDesign, you will be tempted to explore. That natural and healthy impulse should be slightly tempered with the knowledge of how defaults work in this program. Consider the preferences I suggested you change. By setting them with no documents open, those preferences are set for all future documents you create. That’s because many preferences are document-specific.
When a document is open, but nothing is selected, any choices you make for Fill color, Stroke weight or color, or, if the Type tool is active, font or text size, all become the document’s defaults for all future content you create. The scary part? Since nothing is selected, none of these changes are apparent until you create something new by drawing a shape or adding a text frame. Let’s try this.
The usual pitfall is accidentally or absentmindedly setting something as a default. You may later create something and be startled that it looks a particular way or affects other content in unexpected ways. You then not only have to fix that specific object, but you also have to deselect and make that fix again for all your future objects.