My advice is simple. Be yourself. Your style/look should merely express whats on the inside, if it doesn't its fake and lasses will pick up on it (like Russian' said). Werely look at clothes and buy what you like and what suites you. You can augment this by picking parts of your personality you want to express and showing them. For example I'm a bit alternative and have a different taste in lasses from most blokes I know - so I have a labret (centre of my bottom lip) piercing and I wear a pointy stud in it. This highlights that I'm different, but it isn't enough to scare off other lasses. Plus your style is always changing, because your always growing and learning, if it stays the same then you'll just stagnate.

Also I'd just like to say that socially American women are different to English women.