1. Dynamic Spelling (red lines under misspelled words, green lines under repeated words)
(Edit > Spelling > Dynamic Spelling)
2. Info Column + Paragraph Styles (shows which style is being used)
(View > Show/Hide Info Column) + (View > Show/Hide Paragraph Styles)
3. Paragraph Break Marks (indent at the start of every new paragraph)
(View > Show/Hide Paragraph Break Marks)
4. Hidden Characters (representative symbols of white-space characters)
(Type> Show/Hide Hidden Characters)