Hi,
For scoring good in US history and any other subject, I will suggest you following things.

I) Prepare MCQs as much as you can.
II) Time management is very crucial. Each question contain 20 marks so give time to every question.
III) Prepare 25 jargons of every subject. This will fetch you lot of marks as examiner will consider you well versed.
IV) Paper presentation matters a lot.