For a casual outfit with a modern twist, you can easily rock a black crew-neck t-shirt and dark green chinos. Put a more refined spin on your getup by rocking black leather derby shoes. So if it's a warm afternoon and you want to look on-trend without exerting much effort, this ensemble will do the job in no time. Those who wonder how to wear semi-casual style as you make your way through your teen years, this pairing should answer your question.