The main difficulty with assessing Socrates' views of the afterlife is that we have no actual written works by Socrates, only works about him by other people. The portrait in Aristophanes' Clouds being primarily satiric, the major contemporary sources are Plato and Xenophon. In Xenophon, although Socrates is portrayed as not fearing death or any other forms of hardship, the basic theology is closer to Greek popular religion, with a rather indistinct notion of what might happen after death; Socrates is portrayed as seeking death because it is superior to old age. In Plato, Socrates and other interlocutors have various different accounts of death, across different dialogues. Plato's Socrates is consistent with Xenophon's in not fearing death, and seeing it as either nothingness or an improvement over life, possibly a reunion of the soul with God, possibly the soul being freed from the body and communing with the forms, and possibly a cycle of metempsychosis.  Socrates' attitude towards death, though, is best summarized by his concluding lines in Plato's Apology:

"The hour of departure has arrived, and we go our ways--I to die, and you to live. Which is better God only knows."