If you find yourself stuck on an assignment, just start writing, even if it doesn't sound perfect at first. It's easier to write and rewrite rather than trying to get it perfect the first time.
Always be short and succinct. Go through your sentences word by word with a scalpel if necessary.
Try to read the Post with an eye for how their reporters write their stories. The best way to improve your writing is just writing more and reading more.
And when you get an assignment on a deadline, do it ASAP, because missing your deadlines by mistake is the best way to pull your grades down.