In two words personal style is an individual's identity. It typically reflect an individual's lifestyle, attitudes, values and world view.
It also includes ones ways of thinking, and how to behave and dress. Not all aspects of a style are voluntary. Surrounding social and technical systems can constrain the style choice available to the individual and the symbol he/she is able to project to other and to the self.
Simply put, your personal style is not just clothes. Style is a reflection of all those characteristics mentioned above mixed in a very special crazy quilt.
In this way we can say that everyone has his own style, but we cannot describe everyone as a stylish person. A person can be called stylish when all the components are harmoniously pervading each other. When they are "strung" on one's personality and identity and permeated by it , then one will be noticed and remembered.
Think in the context of the above of Marilyn Monroe, the Dalai Lama, Mother Teresa, Audrey Hepburn, Lady Gaga and other celebrities.
To me it seems convenient to divide the concept of "style" into four components;
1) Environment - Where and whom you live with, where you go,culture, traditions, etc.
2) Appearance - This includes your face, figure,proportion, texture and colors
3) Lifestyle - Hobbies, work, pastime, entertainment, status etc.
4) Character/personality - Taste, Habits, preferences, view of the world
When one of these components change so does our style.
In my opinion, the environment is the most important of all these components. If we misjudge the environment around us, we can easily make a wrong impression that may take a long period of time to change.
Admittedly, we can pick a perfectly flattering dress, perfect shoes, hair, makeup, in the best of colors and come in our full splendor, say in a swimming pool. Despite all our efforts, it I unlikely that we would impress someone the way we wanted, Conversely we cannot come to the office in a swimsuit.
Visiting a boyfriend's parents we don't wear the same clothing as we would in a nightclub. For a trip to the theater we would not dress the same way as if we were going to the woods or having a picnic. In countries with strong traditions, no matter how much you want to express yourself, you have to act within the guidelines of the permissible culture.
The conclusion is that before you go anywhere, think about the environment. If you need to make a good impression, but the environment is new to you, gather information in advance about what attitudes and expectations prevail there and dress accordingly. Impressions can and should be managed. This applies not only for traveling to other cities and countries, but for the highest level of entertaining down to visiting a children's party.
The second important thing in the art of looking good, is understanding one's own appearance. Most of us have experienced that when we try to copy an outfit from a magazine or from someone elses, we realize that, at least, something turn out wrong. What looks gorgeous on another , does not necessarily look as good on us.
Why? Because despite the fact that we all have two arms and two leg, all parts of our bodies are very different and differently positioned. Therefore it is important to examine your facial and body proportions and learn how to highlight and disguise them depending on your needs.
Having these two parts brings 85% of success.
Lifestyle and personality often follow automatically and sometimes there is no need to show them at all, for example when wearing an uniform, (but you can still look good if the uniform flatters your body.)
On the top of thee is "ease" - the way you feel when at a place, how you feel in your clothes, the way you behave and communicate. No matter how expensive your clothes are, you will never look good if you feel uncomfortable (unless you are a great actress.)
In conclusion, we can say that personal style is a mix of appropriateness, knowledge of your body and how to dress it. It is also a reflection of you, your personality and your lifestyle.
As you can see, the style is a puzzle composed of many elements which are different for each person, so the style becomes personal.