Scan the right scope
Start with the whole permitted volume for a broad answer, your home folder for personal storage, an external drive for media and backups, or a specific folder for a focused investigation.
Read size spatially
The largest rectangles represent the largest items. You can immediately compare folders that would be difficult to understand from path names alone.
Drill down with context
Double-click a folder to make it the current map, use breadcrumbs to move back, and select any region to inspect its full path and largest contents.
Move from DiskPal to Finder
When you recognize an item, reveal it in Finder. Check that it is the file you expect before moving, archiving, or deleting it.