Each one of you has their own understanding of what is "dangerous". So do the inhabitants of our post-apocalyptic world.
In general, the most dangerous locations are marked by the red sign.
If you are puzzled by the raider's tasks asking you to complete some tasks in dangerous locations, you should head to Pine Woods or Limestone Spires.
When your are looking for rare items or tools, try searching red wood and stone locations, the Bunker Alfa, the Crooked Creek Farm, Floppy with Coordinates locations, etc.