The first paragraph of a Wikinews article —the lede— summarizes the essence of the article.
Prepare
Figure out very short answers to the basic questions about the news event: who, what, when, where, why, how. Remember, your answers have to come from the sources; some answers may be unknown.
Then write
Around 50–80 words, using one to three sentences. Try to answer as many of the basic questions as you reasonably can.
Don't make it a boring list of facts. It's the first thing the reader sees after the headline, so make it interesting.
Later paragraphs in the article will back up or expand every fact or issue mentioned in the lede, and answer any basic questions not answered in the lede or explain why we couldn't answer them.