For me, I use a one-hour skype session to talk every potential client "down off the ceiling". We discuss their idea, and then work together to define a scope I can do for $5,000 in 4 weeks (this is the service I offer at http://builtFromIdeas.com )
Could you go into more detail about how you deal with the initial stages? What if the client wants more, eg. "without this feature it doesn't make sense", etc. Thanks in advance.