Politics Alevel model essay

We've been told to write an essay for homework which will be graded, but I don't even know what it's supposed to look like. How do I get the necessary analysis in? I'd be very thankful for a model paragraph!
Politics Edexcel A-Level, preferred topic would be the US Constitution, but any topic in the spec is totally appreciated.

Hey, I just finished Politics and got an A*. I was fortunate enough to have a great teacher who taught writing v well. I haven't got an essay explicitly on the topic above to hand, but I can PM you one from elsewhere in the spec if you'd like -- lmk