Narrow the subject down.

Keep it personal. Think of a story from your own life, something that nobody else can write.

Follow everything your teacher has told you about essay structure.

For example, if it's supposed to be a newspaper article, begin with the "five W's: who, what, where, why, and why." If it's supposed to be a "five paragraph essay," state your point in the first paragraph--your "thesis statement." Makes three related points in three paragraphs, Then write a conclusion. 

Be sure every paragraph begins with a topic sentence.

If it's a news story, stick to fact, facts, facts. Of course, "something that someone said" is a fact. 

If it's an essay, support every opinion with a fact or an authority.

Bad: "The Houndstooth Growlers played poorly last night."

Good: "The Houndstooth Growlers lost last night, 163 to 15. Team captain 'Sparky' Sperling said 'We really played poorly.'" The score is a fact, and what the team captain said is a fact.

If it is possible, ask a friend to read over your essay before you hand it in. Your friend doesn't need to be an expert on English. The important thing is the "second pair of eyes."