Statistics have shown that for those who take the TOEFL exam more than once. Generally, around 55% will improve their score, whether big increase or just in small increments. That's why it's advisable for students to take the exam early and give themselves a chance to retake the exam if they are not completely satisfied with their score.

Some people take it a couple of times as a practice. Although that's an expensive and time consuming method to prep for your exam.