Taking the PSAT as a freshman...?

My school requires you to take the PSAT as a freshman, sopre, and junior. As a freshman, it doesn't count for anything except you have to be one of the top scorers to be qualified for AP Global History in Spring term... my school is a specialized high school so everybody there is very smart. I took a practice last thursday, and I am taking the real one this wednesday. I think i did really badly on the practice one so I am very nervous for the one wednesday, even though I am usually very good at standardized testing. What is the best way to prepare for it (and quickly) as i really want to get into AP Global??