Some questions to consider:
1. How does the invocation function in the poem? How does it outline the 'plot' of the epic? What is that plot? And how does Milton figure time in these opening lines?
2. How does Milton conceive of his poem in relationship to antecedents? What precedent traditions is he invoking? How does Milton put himself into relationship to those traditions?
3. Why does the action - if such a term can be used in relation to Paradise Lost - begin in hell? How does Milton figure the satanic host? What metaphors or similes does he use to represent Satan? Are there particular passages which you find to be particulary useful in helping to understand Milton's attitude towards Satan? Finally, is Blake right: is Milton really of the devil's party without knowing it?
Watch this space for possible further updates.