Buy a review book and go through it in the days/week before to refresh your memory.
In your essays take five minutes before you start writing to really think about the question and plan what you are going to say.
MAKE A TIMLINE- of major events, presidents, important elections. I found that being able to remember things in sequence and what came after and before and event was very helpful.
Trace Themes- LIke U.S foreign policy, Expansion, Role of government, Minority rights, political parties. Just make general outlines that trace how these themes developed over U.S history. For instance Foreign policy should contain the monroe doctrine, the roosevelt corallary, The truman doctrine ect.
And generally make sure you get a good nights sleep and a good breakfast. Show up early.
