The TOEFL is made up of several sections. However, the sections differ based on the type of test taken. There is the Internet-based TOEFL, or iBT, and the paper-based TOEFL, or PBT. Some testing centers around the world only offer the PBT; however, the iBT is offered far more frequently according to ETS. Check at your location to see what testing options are available.
The PBT tests structure and written expression, reading comprehension, listening comprehension, and writing. The iBT tests reading, listening, writing, and speaking. Because these sections pull from several different senses, it is necessary to practice speaking, listening, and writing English to prepare for the TOEFL.
For the reading section, you will need to be able to read well at an academic level. Work on learning more vocabulary: try to guess the definition for unknown words based on context, and look up the definition to check your guess. Also, reading comprehension is key. Practice reading quickly, and try to summarize sentences and paragraphs in your words as you read.
In preparation for the listening section, immerse yourself in English content. Watch movies, listen to talk radio, and tune in to English television stations. Remain focused, and always ask yourself, "What is the main idea of this speech/dialogue/story?" It is also important to merge the ideas together in your mind to form a logical context. Try to understand the relationship between the words, and predict what will be said next.
The best way to practice for the speaking section is to interact with native English speakers. Engage with an English club, a tutor, or, if in an English-speaking country, anyone you might encounter throughout the day. Discover what grammatical constructions are difficult for you, and intentionally incorporate those constructions into every conversation. Allow others to correct your pronunciation and grammar, seeking to discover the best way to phrase ideas.
Writing often comes last in learning a language, so many of the exercises in other areas will help you here. In addition to those exercises, find sample writing prompts and practice writing out responses. In your responses, avoid using much language from the prompt; rather, put it into your own words. Learn synonyms, the details of syntax, and the way to structure an essay.
The only way to adequately prepare for the TOEFL is to practice.