10 commandments of typography (infographic)

Not mine but so fairly good general tips. I think you can distill it down even more:

• Be careful when mixing fonts that are different 
• Less is more - stay consistent with mood, time, design (be appropriate to your content)
• Make it readable

 DO:

• Know your font families
• Combine a Sans-serif with a serif font
• Combine a serif with a sans-serif font
• Contrast is the key.
• Stick to 2 fonts.
• Combine fonts of complimentary moods and time eras.
• Use different weights of fonts only in the same family.

DO NOT:

Combining 2 similar fonts is not cool.

Don't mix moods.

Avoid: Comic Sans, Papyrus, Curlz, Viner, Kristen, Symbol (well, at least you need for scientific or mathematical writing)