Logo Principles Always design your logos in a vector application such as Adobe Illustrator, and not a raster application such as Photoshop, why?
Logo Principles… Ensure that the logo can be reproduced in a single color, such as black and still be recognizable. What media use B & W?
Logo Principles Bear in mind that the logo may need to be reproduced as small as a postage stamp, so ensure that any fine lines or text will still be legible when scaled down
Location and use Upper left corner of Web page A link to the home page Size: rule of thumb about 74 x 74 pixels
Color Use colors near to each other on the color wheel (e.g. for a “warm” palette, use red, orange, and yellow hues). Don’t use colors that are so bright that they are hard on the eyes. Red on Blue hard to see The logo must also look good in black and white, grayscale, and two colors. Breaking the rules sometimes is okay; just make sure you have a good reason to!
Typography Make sure the font is legible when scaled down, especially with script fonts. One font is ideal, and avoid more than two. Strongly consider a custom font for your design. The more original the font, the more it will distinguish the brand. Examples of successful logos that have a custom font are Yahoo!, Twitter, Amazon, and Coca Cola
Tie to Brand The whole point of creating a logo is to build brand recognition. So, how do you go about doing this? It varies from case to case, but the goal with the logo is for the average person to instantly call the brand to mind.
Amazon A to Z Smile
Relevant
Amazon logo: Jeff Bezos created it. He had big dreams for this business and expected to do huge volume selling, so he renamed his company "Amazon" after the world's most voluminous river. The logo has a very simple design: A small yellow arrow between the first A and the Z letters. The yellow arrow implies that they have everything from A to Z and also represents the smile on the customer's face
Portions via http://www.webdesignerdepot.com/2009/06/12-essential-rules-to-follow-when-designing-a-logo/