The great Disney artist Paul Felix wrote some great notes on perspective and layout years ago. They are full of great information and very clearly written. If you've never seen them before, check them out - even if you're not particularly interested in layout they're full of useful knowledge about drawing.
Links to them at the "Unofficial Paul Felix Blog":
Part One
Part Two
Part Three
Part Four
Or all in one spot at Dan Caylor's "On Animation":
Paul Felix notes