We've said it time and time again: the best way to guarantee a high SAT score is to read more!
Reading more builds your reading comprehension, or the degree to which you understand what you read. Students that read a lot can generally read a sentence or paragraph once and understand what it means. They also usually have good grades in Literature and Humanities, if they do their homework. Students that don't read a lot tend to have poor reading comprehension. They have to read the textbook or assignment over and over to understand what it means, and even then, may not get it all. Correspondingly, they usually have lower grades than students who read a lot.