"Asi" is frequently used to make an example on how something is or should be. Examples: "Asi se hace", "Asi deberias comportarte", "Asi no lograrás nada en la vida", there may be another uses I guess but the most common is that one. "Tanto", I'm not sure if you are referring to the one that is used to compare or the one that is kind of a connector. Examples: To compare: "No estudia tanto como yo" Connector: "El inglés es importante, por lo tanto deberias aprenderlo" "No llores, no es para tanto" "Tanto estudiar me está agotando" "Veo las noticias para estar al tanto de lo sucedido" As a connector I just realized it has a lot of uses :)