This isn't a tutorial but a request for those experienced to share some knowledge. I've seen many multiple story farms but I don't quite understand how to create one. I've seen waterfalls that go down multiple floors to provide proximity to water. Is there a infinite well or pool that needs to be created above these waterfall holes? Also light requirements... I've seen torches on all 4 sides of a block hanging from the roof or glow stone blocks and jack o lanterns to provide light. Do these work? Will things grow faster with these artificial lights around. And can you grow crops without any sunlight at all? What are some other methods? Thanks in advance!
http://www.minecraftwiki.net/wiki/Wheat_farming This should answer any questions you have. Note that redstone lamp farming is prohibited.
Would anyone care to post their 20x20 plot layout? And do the waterfalls not work because the water needs to be caught?
Water falls work but I do not suggest them. It is much easier to make single block holes to place water in and cover them with a lily pad or half block.