Less is usually more.
1 Clear visual hierarchy
Headings, sub-headings, paragraphs…
2 White space
Give eyes a breather
Use easily legible typefaces, have good contrast between text and background, lines not too long…
4 Alignment, consistency, simplicity
Think of a well-designed supermarket
5 Golden Rule (for information design part)
Remove ink, wherever possible, within reason
These “rules” can sometimes be broken, but you should do so knowingly.