Register for the TOEFL PBT and you will automatically receive a free kit of TOEFL practice tests. This kit includes two sample exams, listening material and scoring information. Take advantage of these resources to prepare for the test. The official TOEFL site has free sample questions, as well as free sample writing topics in PDF form. These are available without registering for the exam and are good resources to determine if you are ready to register for the exam. However, they are not nearly as comprehensive as the kit that comes when you register for the exam.
Hire a teacher or attend a TOEFL preparation class. This can be done through a private language school or by contacting a teacher directly. Work with a TOEFL preparation book. Longman, Barron and Kaplan are all publishers that offer TOEFL preparation books.
Immerse yourself in the language. Read books in English. Practice your listening comprehension online. News websites such as BBC and CNN offer online recordings of news in English that you can listen to.