Finding out the personality of a person can be difficult. You cannot make a decision about a person simply by looking at them in one instant. There are multiple phases and plus, the person may have a bad personality but be good at heart. This is why even psychologists take time before pronouncing or commenting on a person’s personality.
You need to understand that personality is the basic impression of a person or the way he dies the things. It is not the actual things, which could be opposite to his personality. This is why it is best to evaluate e a person based on his actions rather than judge them on their personality.
Only if you are a good judge of personality! Even psychologists, whose job it is to discuss and pronounce upon personality, often use sophisticated personality tests before describing someone's personality, or personality type. Judge a person by what s/he does rather than what s/he says, and don't rely on the one instance.
By 'personality' many people actually mean 'charisma' and that is a very different thing. Those in the performance arts or in sales may have charisma. The wide smile, chuckling voice, and kind crinkly eyes sympathising with you may not relate to kindness or sympathy in real life, although this person will often be described as having 'a great personality.'