Can’t design? Buy The Non-Designer’s Design Book. Fabulous thing, it explains the basic rules, and you can figure out much of the rest from there.
The quick summary: apply Contrast (be brave: make differences obvious lest they appear to be mistakes), Repetition (repeat for consistency where possible, and of course use paragraph styles in Word or InDesign or whatever), Alignment (most things look better lined up with something else on the page, so use those invisible guides) and Proximity (white space is important). Extend these rules through every layout and in combination with one another. More, much more, in the book, with a great many examples of what works and what doesn’t.
(Oh: don’t centre anything! It ruins any chance for alignment along left or right margins and creates ugly white space on either side.)
Anyway, buy the book, or arrange to be given it as a belated birthday present.