Some typography “best practices”
- Have a comfortable measure (66 characters is by many regarded as ideal)
- Whitespace is good. Especially the margins are important.
- More important than whether you have black on white or white on black is that the contrast shouldn’t be too high. In fact, black on white is IMHO too sharp, dark dark gray on white is better. (Only applies to screen, black on white is good on paper.)
- Whether a font is easy to read has a lot more do with whether if it has serifs or not.
- The size of the font should be appropriate, not too large and not too little. (My opinion: anything bellow 14px is way too small, and 16px seems to work well very often.)

Stuff I personally prefer:
- I prefer a larger line-height to a smaller one
- Narrower measure than what most sites have. (I despise websites that have text as wide as the browser viewport.)

<a href="webtypography.net">The Elements of Typographic Style Applied to the Web</a> has some useful resources. If you want to learn about typography I highly recommend the book Thinking With Type by Ellen Lupton. (Once that books converts you to a typography geek, get The Complete Manual of Typography by James Felici.)