Listen and learn
Listen to all kinds of music. To earn a living arrangers and composers must be able to write in just about any style. If you can afford it, get out and attend live music events and hear as much variation of style as possible. Classical old and contemporary jazz, rock, folk, in fact just about anything. These days there's a wealth of recorded material available on the Internet in all styles, old and new. Select the good stuff and download it. You don't have to like all this music but you should absorb it. It will all resurface when you need it.
