Well, first off, boring writing covers a multitude of sins. Without looking at your writing (which I can’t do), I can’t tell you why it’s boring exactly, any more than if you call up a doctor and tell her you don’t feel well, she can tell you what’s wrong with you exactly. The differential, so to speak, is vast. This is why you need someone — a teacher, friends, ideally a class of writing students — reading your work and giving you feedback.
If you are convinced that your writing is boring, ask yourself a few questions:
Are you including details that aren’t necessary to the story, just to pad out scenes and make them seem longer/more important? Keeping in only details that matter to the story speeds up the pacing and keeps the story interesting.
“Joe got up and brushed his hair and then his teeth. He chose a blue sweater to wear and made bacon, eggs and toast for breakfast. He got his briefcase and opened the front door. He went outside and locked the door behind him. He went to his car and turned it on. He drove to work. It took twenty minutes.”
can be edited down to this:
“Joe went to work.”
Unless there is something remotely important about the tooth brushing, the breakfast food, or the locking of the front door, skip it all. It’s not interesting or significant to the story.
Are you overstating characters’ emotions in order to make everything seem more dramatic? Trying to make a scene seem more dramatic by adding in overwrought detail often has the opposite effect.
Are you using redundant language in order to add emphasis? For instance, “‘This is the worst day of my life,’ sobbed the wretched girl.’” We know she’s wretched from the sobbing and the fact that it’s the worst day of her life. We don’t need that extra adjective; once again, it slows down the pacing.
Does every scene you’re writing serve more than one purpose? A scene that tells you something about a character is good; a scene that tells you something about a character and also moves the plot forward is better.
Are you writing in the passive voice? Avoid passive voice; use active voice.
Are you being self-indulgent? Every writer has to love what their writing, but it can become a problem when you’re in love with what you’re writing. Especially if you’re in love with your main characters or in love with their relationship with each other. There’s a fine line between romantic and soppy. Also, you have to make us, the readers, care about your characters before we are ever going to care about their relationship with each other. Zoom on back up to the question above about characters and make sure yours are ones that we are going to love enough to follow them through the whole story.