For instance, a friend who always has a huge smile and a positive attitude has a brand, and a friend who is always 15 minutes late, so you start telling her a time that is 15 minutes earlier, has a brand.
Professionally we get hired, fired, promoted, selected, headhunted etc. based on our perceived brand.
The key is understanding those perceptions and acting on them. Once you know, you can become conscious about the brand you are communicating to the world (i.e. If you don't want to be the person who shows up 15 minutes late, focus on always being on-time or early.)
William Arruda's article, Five Ways to Learn What People Really Think About You gives a five step process to determining how we are perceived.
How do you think your friends / colleagues / family would describe your brand? How do you want to be described?