Detailing my philosophical beliefs is no easy matter; as I wrote nothing myself, we must rely on the (sometimes) conflicting reports of Xenophon and Plato. There is ongoing debate as to what, exactly, I believed as opposed to Plato, and little in the way of concrete evidence when demarcating the two. There are some who claim that I had no particular set of beliefs, and sought only to examine; the lengthy theories I give in the Republic are considered to be the thoughts of Plato. Others argue that I did have my own theories and beliefs, but there is much controversy over what these might have been, owing to both the difficulty of separating me from Plato and the difficulty of even interpreting the dramatic writings of Plato. Therefore, it is very important to keep this in mind when reading the presentations of my thoughts; none of it is agreed upon, and all must be taken with a grain of salt.
Evidence from the dialogues suggests that I had only two teachers: Prodicus, a grammarian, and Diotima, a priestess from Mantinea who taught me about eros, or love. My knowledge of other contemporary thinkers such as Parmenides and Anaxagoras is evident from a number of dialogues, and historical sources often include both of them as my teachers. Apollo himself may be considered one of my teachers, as I claim (in Plato's Apology) that my habit of constant conversation was obedience to god.
People interested in thinking about thinking...
Apology, written by Plato
Crito, written by Plato
Euthyphro, written by Plato
Phaedo, written by Plato