The Ten Commandments of Typography

The Ten Commandments of Typography by Paul Felton
1. Thou shalt not apply more than three typefaces in a document.
2. Thou shalt lay headlines large and at the top of a page.
3. Thou shalt employ no other type size than 8pt to 10pt for body copy
4. Remember that a typeface that is not legible is not truley a typeface.
5. Honour thy kerning, so that white space becomes visually equalized between characters.
6. Thou shalt lay stress discreetly upon elements within text.
7. Thou shalt not use only capitals when setting vast body copy.
8. Thou shalt always align letters and words on a baseline.
9. Thou shalt use flush-left, ragged-right type alignment.
10. Thou shalt not make lines too short or too long.

But you can break all these rules...