"Para" can come before an infinitive that explains the purpose of the main verb: In many cases this would answer the question "What did you do it for?" eg. I went to the bank in order to take out some money. -Fui al banco para sacar dinero- In English the "para" would be translated as "to, in order to, so as to, in order not to, so as not to. "Por" is used to explain the reason or cause of an action. Answer the question "why is this thing done for? Whereas "para" is used to explain the purpose of an action. eg. I will answer this question for your own sake. - Contestaré esta pregunta por tu propio bien I've taken the information from this site, please refer to it for further exemplification. http://www.lingolex.com/swom/wom-porpara.htm

Por y Para estan basadas en el sentido que quires dar a la oracion si dices: Hice algo para ti. I made something for you. "Para" is used to say "for somebody" or to "somebody" Hice algo por ti. I did something because of you. "Por" is use as cause and consequence of somebody. Others example: To you = para ti. because of me= Por mi. forever= por siempre o para siempre [ambas se aceptan]