1. Write. You need to do something a LOT to get good at it. That goes for everything, including writing.
2. Read. The best and only way to really study the craft. Don’t only read one type of books or one genre. Read a bit of everything. Study, reflect, analyze. To stay reading a lot always bring books with you. Keep books on your phone (if you have a smartphone), get a e-book reader like a Kindle.