Read your fiction aloud. Don’t do this on an early draft, or you will drive yourself crazy trying to tie plot threads together and fleshing out characters. Wait until you are editing sentences, single words even. Then read your piece aloud. It doesn’t need to be read to someone (though it can be), but by turning the words on a page into sound you will notice so much more. Hidden grammatical errors will pop up, awkward word choices will be revealed, and boring, stilted dialogue will fester. Really, try it. It took me a long time to give it a shot (I can’t remember who recommended it to me), but it significantly improved my drafts. After all, which do you expect to help more: reading a draft for the fifth, sixth, or seventh time in your head or giving real voices and sounds to your narrative?
Experience other forms of storytelling. I write; that’s my form of expression. But there are so many other types of stories to be had. Watch a TV show, see a movie, listen to an album, read a novel, play a video game, admire a painting, dive into a comic book, hear a spoken word poem, check out an anime, sit around a campfire and take in a ghost story, go see stand-up comedy, try to talk your way out of a speeding ticket. Narratives permeate the world around us, but I’ll be the first to admit I subconsciously limit myself in what I consider when I write. The written word has so much to offer, but it doesn’t have everything. When you are burned out and can’t write another word or you just need a new source of inspiration, give a different medium a shot.
Write a Wikipedia article for your characters, places, and events (it could be a regular encyclopedia article, but this it is the twenty-first century). This is a longer exercise, and I find it to be particularly helpful on stubborn stories that refuse to move forward. Separate a character’s lifetime into the early years, middle age, and late life. Fill in those categories with a few lines of description, circle important nouns, and start new articles for each of those nouns. The circled will act as the links in a Wikipedia article. After a bit of work you’ll have a network of people, locations, and events with the basic framework for the world of your story. You can work on this network as long as you like, from creating a scant few connections fleshing out minor characters to developing a rich history of the people and lands that populate your work.
Give any or all of these tips a try. Hopefully they work for you, and if they do, pass them along down the line.