Applying some interpretation to your question, I would say that by far the most important way to find rares and legendaries is the Auction House. Once you are familiar with the stats that matter to your class, you can easily search for low buyout items that are typically way better than what you will find via trial and error searching. I'm still in the mid levels, so maybe the going gets tough near 60, but so far I have found various items that are a steal.
Beyond that, it doesn't make much sense to use magic find for get items for crafting since while certainly helps your luck, trash items on the AH are also in high supply.... and why are you crafting in the first place when you can buy such awesome stuff for cheap anyway?
Others suggest that magic find may be used to build up your cashflow early on, but I haven't found that to be a problem - and... I've made way better money, at the Auction House.