I was often intrigued by the combination of impressively well designed logo symbol and poorly chosen typography. Its like dressing up for a party and not choosing the right clothing.
Typography is picture of words. The letterforms work together to transmit a message. The attitude, history and culture of a company, organization or person are conveyed through the font used for the logo. The shape of the letterforms must work well with the logo symbol to create a whole, they need to emphasize and enhance the character and the personality of the logo.
Coming back to the clothing metaphor, the typography will either make the logo a success in time - the right "clothing" will be admired five years from now, or be very trendy, a hit at the moment of launch, but get tacky in time and needed to be changed.
To better understand typography we need to look at a short classification and their main characteristics. When designing a logo its easier to choose an appropriate type class narrow it down and then select your font from there.
Humanist: caligraphic forms
Font samples: Centaur (preview), Verona
Old Style: style of font based on ancient Roman inscriptions, these fonts are generally characterized by low contrast between thick and thin strokes, bracketed serifs, and a left-leaning axis or stress.
Font samples: Garamond, Goudy Oldstyle, Century Oldstyle, Palatino, Sabon, Caslon (preview)
Transitional: proportional refinement, medium contrast between thick and thin strokes, less left-inclined stress than earlier Old Style faces
Font samples: Baskerville, Fournier, Bell (preview)
Modern: heavy contrast
Font samples: Bodoni, Modern, Walbaum (preview)
Slab Serif: heavy square-ended serifs
Font samples: Rockwell (preview), Memphis, Clarendon
Lineale or Sans Serif: without serifs
Font samples: Arial, Helvetica, Verdana, Futura, Univers (preview), Franklin Gothic
Font samples: Palace Script, Young Baroque (preview)
Digital: digital forms
Font samples: Oakland, Isonorm (preview), Modula