Logo design is all around us. To the general public, logos serve as an instant reminder of a company or a product; to the client they're the point of recognition on which their branding hangs; and to us designers they represent the challenge of incorporating our clients' ideologies into one single graphic.
A logo must be simple. A simple logo allows for easy recognition and allows the logo to be versatile and memorable. Effective logos feature something unexpected or unique without being overdrawn.
A logo must be memorable. Following closely behind the principle of simplicity is that of memorability. An effective logo should be memorable and this is achieved by having a simple yet appropriate logo.
A logo must be enduring. An effective logo should endure the test of time. The logo should be 'future proof', meaning that it should still be effective in 10, 20, 50+ years' time.
A logo must be versatile. An effective logo should be able to work across a variety of mediums and applications.
A logo must be appropriate. How you position the logo should be appropriate for its intended purpose.