Where may I find a full discussion of these and their usage? I find the reduplication in sentences (say- lo and a el) particularly confusing.
jdabell -- If you continue studying on DL, this link will be of great benefit to you. You can get good answers there. You can get get some good answers from fellow Dl users, but you can also be confused. Sometimes DL discussions are the proverbial "blind leading the blind." ;)
The repetition of the pronoun most often is not necessary, but we use it in Spanish to know the gender or for emphasis. For example, the phrase: "Say him something" can be translated as "Dile algo", but without a context you don't know if you are talking about a male or a female one, so you can say: "Dile algo a él" or "Dile algo a ella"