Hermione's daily style is pretty understated. Much like her personality, her clothes are practical and logical. In the winter, she keeps warm in fitted but interesting sweaters and basic corduroy pants. Although her taste is simple, it doesn't lack style and there is always something interesting about the choices in her clothing. She rarely sports any jewelry or accessories, aside from a time turner, of course.
Ron's style is hardly that- his clothes are likely all second hand, or in the case of his sweaters, knit by his mother for him. His clothes tend to be ill-fitting, likely due to the fact that they are hand-me-downs from his (many) older brothers. They also tend to be in fairly poor taste, not really sure why that is.
Harry, in the books, is often described as wearing ill-fitting clothing that has been passed down from his cousin Dudley. In the films, this isn't the case at all. Harry's clothes fit well and look far from worn. His look is decidedly more athletic than Ron's, but still casual and comfortable.
Even though we've watched them grown up into adults, I'll still always remember the three of them as they were in the first movie.
Ron with his chipmunk cheeks:
Hermione's ridiculous bushy hair:
And Harry's wide-eyed innocence:
Thanks for the memories, kids- it's been a great ride!