A cottage industry has been built up around people giving writing advice. I've never been one for How To books or Writing Tips. I believe that writing is something you either can or can't do - it can't be taught. Oh, you can teach someone correct grammar, punctuation, word choice, but you can't teach them how to feel the rhythm of good prose, or hear the heartbeat behind the words on the page. It's impossible to even describe, so how the hell could you teach it?
In my opinion, the most valuable writing tip in the world is this: just fucking write.
However, to supplement this you need to have a wealth of experiences in your back pocket. I didn't start writing seriously until I was well into my thirties, and there's a good reason for this: until then, I hadn't lived enough of life to have a good enough stock of material to draw upon for inspiration. I didn't know enough about the world, about people.
So here's something I've been known to tell young writers when they've asked me for advice:
Step away from the desk, get out into the world. Take a bus to an unfamiliar district. Get lost in a city you don't know. Sleep with a whore. Have a fistfight. Punch a goat. Consort with unsuitable people. Argue face-to-face about something you believe in. Go to sleep in a strange house. Wake up in a gutter. Climb a mountain. Lie down in a wood or a forest and cover yourself in fallen leaves. Spend time with someone you despise. Spend time with people you love. See the stars from somewhere that isn't your home. Open your eyes. Expand your mind. Live a little.