OK, in english you say: In spanish you say: He told her a secret. Él LE dijo un secreto. I could say that in spanish we usually add some words because of the grammar. OK let me show you, imagine this case, let's remove LE: Él dijo un secreto. If you say something like this it means that he just say that secret, now, if you add LE see: Él LE dijo un secreto: It means that he told a secreto TO SOMEONE. When I was a child and I was around 7 my teacher always said that when you don't know if use LE or not question to you: ¿A quién le dijo (and the "predicado")? so ask in these case: ¿A quién le dijo un secreto? Answer: a alguien, so if wwe know the answer you have to put LE.