I am not a designer. In fact, I'm barely a writer. But I just got copied on an email from Anne Peck Gibbons on the rules for designing a logo. I think it's good stuff.

1. Logos are graphic. They are not illustrations--they are best when developed like a branding iron.
2. Logos are one or two color--to save printing and production costs for our clients.
3. Logo colors don't touch--because when you convert to black and white, grayscaling is required
4. Logos are solid ink (PMS) colors. They do not have gradients-gradients do not translate into all production environments
5. Logos are readable when reduced to 1/2 inch in height.
6. Logos are shapes. Lines, when reduced, disappear.
7. Logotype designs are exceptions to some of these rules.

So, there it is. Hope it helps.