How do you find boutique consulting firms to see if they’re a good fit for you?

Tough question. Unlike investment banking, there is no centralized database of boutique consulting firms. They're tough to define (since there are countless one-man consulting shops). The
Vault Guide to the Top 50 Management and Strategy Consulting Firms, 2009 Edition is a good start. Google Search is another resource. Finally, there are many forums where you can receive advice (WallStreetOasis Consulting Cabaret and Vault Consulting Message Boards among them). I'll be writing a short article on good consulting forums soon.