Though there are tones of theories about "when to use a preposition", the best thing to do is to learn "what verbs use which preposition". Prepositions sometimes are the same in English and Spanish. I go to the office. Voy a la oficina. Sometimes both, English and Spanish use a preposition, but it is not the same preposition: The comments consist of... Los comentarios consisten en... Sometimes the one language, English or Spanish, will use a preposition and the other will not. She serves God. Ella sirve a Dios. Wait for me Espérame. Sometimes the use of a preposition will require a different verb in either language. Compare: I am interested in History Estoy interesado en la Historia. (Both English and Spanish use the prepostion "in" (en) for "to be interested"). But: Me intereso por ti (Literally "I interested for you") I care about you. My recomendation is to learn the primitive (meaning "the most basic") meaning of a preposition and then, it will be a lot easier (you can always make mistakes, but it will be less likely) to decide when to use a preposiotn and which one should be used. For example, if you think of the verb "to go", you have following possible options: I go to France. (France is the destination) I go through France (France is neither the destination nor de initial point) I go from France (France is the initial point). "to, though" and "from" are all correctly used with the verb "to go". So try to read books or listen to music and learn what prepositions can be used with what verbs and what are the different meaning that the prepositions provide with that particular verb.