The usual advice I mete out --only when asked, of course *grins* -- is to write a lot and read a lot and then write some more. It is sound advice, and I'm certainly not the only one who has offered it. But as I look back, I think my beginner already knew to do those things. We all know practice makes you better at what you do. And most writers I've met are avid readers first.
The other thing, though, the thing we don't talk about as often, is the courage it takes to write. Facing down a blank page can be like standing on the high dive. Maybe it's your first time, or maybe you've taken the dive a thousand times before, but each time there's a thrum in your ear, a roiling in your gut. You know you can do it, or you think you can, and the water is mirror smooth and blue and inviting. But it is a long way down. And if you've done it before, you know it can go wrong, and the smooth blue water will feel like concrete as you crash into it.
My advice is do it anyway. Close your eyes and jump. Pull out the stops and write with your whole heart, your whole being. All good writing comes from this, the thrilling jump forward, the deep dive, the resurfacing.