Give the story a totally unexpected twist. Make something happen, out of the blue. It's your universe! Throw in a random character, maybe your main character's long lost twin, or an old enemy from years ago-someone interesting. Or burn the house down! Not actually, unless that would make your story more interesting. But do something wild. You can always delete it, or tone it down later on. Let go.
Maybe throw a challenge at the character. Have them face their fear, external or internal. Kill someone. Reveal a deep dark secret. There's plenty of ways, just experiment. Good luck!
That's not much to go on! What kind of story is it? Fiction, Non-fiction, Reference? If it's fiction, try adding some characters that are fantasy characters for yourself. What do you want to be. What did you what to do but haven't had a chance to do. Things like that. Be more descriptive of the characters. Working a little on character development will open up a thousand doors and possible plot lines. There are a million things to try in fiction because everyone expects to be wowed but fiction. The sky's the limit! Go for it! Don't try to wow everyone all the time. Just please yourself at first.If it's non fiction you must use facts. One way to be more interesting is to be more descriptive and use more details if you have them. You can do some research for those details. For example if you are writing about a bus, what kind of bus, how many people does it carry. What color is it. Get some details from other sources like the manufacturer or a bus expert like a mechanic or the engineer who designed it.If you go that far then you have entered the realm of Reference. And you might as well write a repair manual for that bus.I hope this helps.
Best time to add a unexpected event could route your story in a different way twists and turns make the greatest stories of all
Exhilarate your story everytime you write.....always read books and practice writing....
Put suspenseful things in your story. (Such as being attacked by aliens!)