Where many people come short is placing all the emphasis on developing a super cool logo, without thinking of how it will be pulled through to the overall brand look and feel, without thinking about how it will translate across various media (for example on the web, in print, branding and signage) and without thinking about whether or not it actually has anything to do with what you do. So, you’ve had a thing for butterflies all your life? That doesn’t mean your logo should have a butterfly in it. Unless you breed butterflies. Then, by all means, add a butterfly.
Colours, fonts, shapes and textures should all be thought about during the brand development phase – not only once you start implementing your brand into marketing material. That will just create an unidentifiable mess and you’ll land up diluting your brand before you even start getting it out into the market.