I am working on my first multi-tiered app and writing the classes from scratch. I am looking for some good ref. materail for VFP. Is there anything recommended besides the VFP help file?

I am mainly concerned with dealing with the data. I know the data layer needs to be totally separate from the business layer and so on. I am a little unclear about how to pass the data back if I need the results from a large query. Would it be best to use something like XML? What does everyone else do???