They say you never get a second change to make a first impression. A good logo design is, in most cases, the first impression a new client or prospective buyer has with you and your product. With a good logo design, people can gravitate to you over your competition (the one with the not-so-imaginative design). A clever use of fonts, a good icon or mascot and a good array of color choices can make a huge difference when creating the best look for you.
Once you establish that perfect logo for your business or product, now you need to pair it with a good design identity or branding. Many big companies have style guides created in order to make sure the look and feel of their company flows and balances with their logo. This is very important to do in order to create a style that is all your own and one that people can identify with.