Most people claim they don't make judgments about people based on appearance, and most people who say that are lying. 

'First impressions' became a term for a reason. Everyone knows appearance counts in first impressions, and first impressions count overall, that is why it is better to wear a tie to a job interview than pajamas but how much are people really able to tell about someone else based on physical aspects, aside from whether or not they are wearing pajamas instead of a tie or if they look like George Clooney? 

A 2009 study examined the accuracy of observers’ determination about 10 personality traits of people based on nothing but full-body photographs. When targets’ posture and expression were constrained - the standardized condition, where the photograph was posed to the researchers' specifications - observers’ judgments were accurate for extroversion, self-esteem, and even religiosity.

When the subjects were photographed with any pose and facial expression they wanted - the spontaneous condition - judgments were accurate for almost all of the 10 traits examined. Lens model analyses, which describe how people perceive an unobservable (distal) criterion through observable (proximal) cues in statistical terms, results in the conclusion that both static cues , like clothing style, and dynamic cuesm like facial expression and posture, helped people deduce accurate personality-relevant information.

So 'the clothes make the man', as the saying goes. You dress to be like the person you want to be and observers use this information to form accurate judgments for a variety of traits. What it also means is that you can change how people view your personality and then maybe your personality itself.  After all, if you want to be treated like a wealthy, intelligent person, and you dress the part and people treat you that way, eventually it will become part of your self-image; who you are. Want to experiment? Dress like a hobo and wander around the streets of a city and people might be all wrong about your  agreeableness, emotional stability, openness, likability, and loneliness but they aren't wrong for making those determinations - most hobos are not conducting experiments.

"As we predicted, physical appearance serves as a channel through which personality is manifested," say the authors. "By using full-body photographs and examining a broad range of traits, we identified domains of accuracy that have been overlooked, leading to the conclusion that physical appearance may play a more important role in personality judgment than previously thought."

Citation: Laura P. Naumann, Simine Vazire, Peter J. Rentfrow, and Samuel D. Gosling , 'Personality Judgments Based on Physical Appearance', Pers Soc Psychol Bull, December 2009; vol. 35, 12: pp. 1661-1671 doi: 10.1177/0146167209346309