In the TOEFL speaking section you are given a statement of question and you have to prepare a ‘mini-presentation’ on that topic. You need to be able to express your opinion in clear and fluent English. For example, they might ask you you think about ‘global warming’. So in order to prepare for the TOEFL section you should take part in ongoing forum discussions where you can learn how to practice expressing your opinion. In addition, you can start a forum discussion by asking a question such as this: Do you work to live or live to work?
TOEFL listening lectures: A lecture in biology class