When I was studying to achieve the FCE i had the terror of not passing it as i had been working hard for months. The day of receiving the marks arrived and... I passed it! But that is not the point of the post, as I would like to explain how did I prepare for the exam.
First of all, if you don't want to go to an academy to prepare it, is read a lot and become rich in vocabulary. I would also reccommend you write down the words you don't know in order to learn them. Next is to study the grammar and phrasal verbs as this is tested in some parts of the official exam. You may want to practice some listening also by listening to music or watching films in English. This is an interactive way to learn and very effective.
To practice the papers of the official exams you can find practice books for the First in libraries or bookshops. Each book has between 4 and 8 tests with all the papers, answers and a CD to do the Listening part of the test (which is the last part). Once you've made a test you can correct it with the answers that are included in the book and, i'll reccommend you, to write down any phrase, word or topic that sounded different or unknow.