Makes impression.
Simple.
Unique.

Simple design – Must translate well in color, black & white, grayscale and shrunk down to 2 inches. You don’t want bevels, filters and excessive gradients. Think of all the large corporate logos, what do they all have in common? Simplicity. Sprint, IBM, Microsoft, Yahoo…all basic but original.
Composition – You want your logo to be able to stand on its own as a design. You typically don’t want any kind of border as this limits its appication, you want the font to correspond well with the pictoral logo(if you have one), meaning if you use a script font, you probably shouldn’t have a picture of a butcher.
Must make sense – If you sell computers you shouldn’t use an image of a cat. The image you project should remind the customer of your service. You do landscaping? Use flowers. Do you cater dinner parties? Have food or plates. Or use something simple like monograms.

I would say, content ,design, and color.