Don't overuse cliches and stereotypes. It makes the story seem unoriginal. Try to come up with fresh and unique ideas and storylines.
One big thing to avoid is having a confusing plot. If the story is hard to follow, readers will lose interest fast.
Don't ignore the scientific basis. Even if it's fiction, you need to have some level of plausibility. And try not to make the technology or world-building too confusing for readers to follow.
Avoid being overly descriptive and bogging down the story with unnecessary details. Let the plot and characters drive the narrative forward.
Try not to have overly predictable plots. Keep readers engaged by adding unexpected twists and turns. Also, steer clear of cardboard characters - give them depth and complexity.
Avoid info dumps. Don't overload your readers with too much background or technical info all at once. It can bog down the story.
One thing to avoid is overusing cliches. YA readers want fresh and unique storylines.
Avoid making the plot too predictable. Readers want surprises and unexpected twists to keep them engaged.
One thing to avoid is having one-dimensional characters. Both the romantic leads should have flaws and depth. Also, don't rely too heavily on external conflicts to drive the relationship; internal struggles and emotional growth are crucial.
Well, one thing to avoid is overly controversial and sensitive subjects that might alienate a large part of your potential readers.
You should avoid cliches and jargon. Cliches make your writing seem unoriginal, and jargon can confuse readers who aren't familiar with the specific field. Also, try to steer clear of overly complex or technical language unless it's necessary for the context.