Being asked to define the elements of personal style is a lot like being asked to define the elements of a great meal: the mix of flavors, colors on a plate, and the sequence of courses. A great meal is certainly more an experience than an object, and so it goes with personal style.
Everyone I know or have known who has what I think is great personal style is not just playing dress-up dolls with their wardrobe. They are on some deep level telling a story to the outside world about their inner selves. Great personal style is the convergence of knowing who you are (you need to figure THAT part out first) and then in effect wearing what you are. Personal style rarely if ever has anything to do with being "in fashion" or "on trend."
Being "on trend" means that if short voluminous skirts are the trend of the moment (they're not) you might go out and buy up several short skirts into your wardrobe and wear them until the fashion magazines and the celebrity weeklies gave out a different signal about the volume in skirts or the length of the hemline, upon which you would go and invest in that newer look. Now, trends can inform how we dress, and they are important (the length of hemlines has been used for years to judge the health of the economy, go figure), but someone interested in cultivating style will never get to their perfectly stylish self solely by following trends in fashion...in fact following trends alone will ensure you never get there! So what's a woman or man to do, you ask?
1. Check in What do you like, what pleases you? I wear a perfume that I've worn since I was old enough to carry it off. I first smelled Opium in a department store in Walnut Creek, California when I was twelve years old. It was the late seventies, and at the time, many reasonably good scents were sold off of drugstore shelves. Only the really top fragrances were carried in department stores, so I knew this scent was special. It smelled of mystery, silk pajamas and incense (what an image!). ANYWAY... I was intoxicated, but at twelve years old, I had the good sense to know I was in way over my head. All my girlfriends at the time wore a powdery cologne called Loves Baby Soft. As you can imagine by the name, there was an ocean of difference between the innocent Loves Baby Soft and and the seductive Opium, so I earmarked it and moved on. I remember thinking that I'd have to be at least 20 years old to carry that fragrance off (20 seemed SO old...) And when I revisited it again in my 20s I knew I still wasn't yet woman enough to carry it - it would have to wait again. I did buy it for myself on my 30th birthday. I have worn it everyday since, and it still smells completely wonderful to me. This fragrance is a part of my personal style, and has become over time one way in which people who know me identify me.
2. Think about who you are Do your clothes and your look tell that story? I have a dear friend who I see occasionally. Steve keeps an apartment in the city with his wife, but spends a good part of his week out on Long Island painting. His paintings have a rugged refinement - landscapes, deep emotional sunsets and sunrises among other topics. Every time I see Steve I am reminded of the voice his paintings have by looking at him. His clothes are simple choices, well worn-in, but never worn-out, rugged but refined. Everything about him from his haircut to his choice of jacket matches, everything connects and there is always an easy harmony -- just like his work. He looks literally as though he stepped out of his own canvas, and wandered into the world. To me, Steve has great personal style.
3. Be consistent As you evolve over time does your look and your wardrobe fit your lifestyle? A word of caution here: being consistent does not mean being fixed. The pace of change in our world today is dizzying, life demands different things from us constantly, and as the world around us moves and changes quickly, it seems to call us to do the same thing. How does someone change yet stay consistent over time? Knowing who you are, as an element of personal style, is critical to steps one and two, but it is most dynamically at play here is step three. Knowing who you are at a core level and staying true to that all the while embracing change within yourself and the world around you is probably the synthesis to great personal style.
I know I haven't given you any hard and fast rules here such as "V necks are more slimming than crew necks" etc., because I don't think personal style is about rules. Yes, it's nice to know what flatters you, and if you honestly don't know, ask someone you trust to give you some feedback. But beyond looking good, personal style is really about being true. True to yourself. Your personality, your psychological age, your physical age, how you view yourself in the world. All of this comes together and gets communicated outward through our appearance, from how we choose to wear our hair to what watch we carry to our clothes and shoes.
The inside informs the outside - not the other way around. That's the real synthesis of style.