The absence of an efficient guide to the prepositions and conjunctions in English, certainly a drawback in the learning process, has led me to dedicate hundreds of hours to this project. This work is above all, a reference book, meant for both foreign and native students and teachers who must understand how the English prepositions and conjunctions work so they can adopt an efficient learning and teaching method from the start. It must be remembered that students will never learn to construct a sentence correctly unless they know what to do with the prepositions or the conjunctions. This book is not a novel to be read and put away. Only through repetition and constant reading and even memorization of idiomatic expressions, formulas and verbs followed by their prepositions, would you succeed in understanding both these parts of speech. A native speaker of any language considers this topic irrelevant. However, you as a foreign student must understand how the English prepositions or conjunctions work and thus, avoid translating word for word. If you choose this easy and effortless way out, the result will almost always be frustration and disappointment. Aware of your difficulties after twenty-five years of teaching English to Spanish speaking students in Spain, I have made a unique effort to explain to you, my way of getting across to my students that there is no secret or difficulty in the understanding of these two parts of speech in English. This tool will serve as your teacher who will always be there to assist you when you need help.