Not much is necessary, actually. You have to write good content that you are passionate about. It's very simple, but people usually make it complicated because they create accounts here to earn money. This shouldn't be your main goal. I highly suggest you start by writing a few posts about things you like. In fact, just by writing you will learn a lot about topics you are interested about.
So it's a two-way road: you write to share knowledge and you acquire knowledge during the process. It happened to myself already.
And don't write for money: write for passion and the money will come later.