Advise for Choosing a Mortgage Lender

Will be looking into a jumbo loan for a new development condo and was wondering how folks went about choosing their lender and had some questions along those lines: 1) How many lenders should I work with? How important is it to work with a preferred lender? 2) How much can rates and fees vary between similar institutions like Wells Fargo or BofA? How about between people within the same institution? 3) Given comparable rates I would think service, responsiveness, and timeliness would be key. Going back to rates and fees, say you find someone you like working with but who doesn't have the best price. Will most offer to match another rate you are offered from a competing firm? 4) Any other important considerations, especially with the new mortgage rules?