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I have an interview tomorrow with my dream firm, it is a boutique firm in the city I want to live (top firm in the city for this practice area), and my credentials and background is a perfect fit. I worked at a small firm in that practice area this past summer which made me certain I only want to pursue a career in a boutique firm (even to the point where I am not excited about a CB at a T100 firm since I can't specialize as a summer associate). I am trying to figure out how to convey to this firm in 20 minutes not only how great a fit it is for me, but also how great a fit I am for them and would dedicate myself 100% to that firm without the need to experience other practice areas. Should I be careful that my enthusiasm for that firm will be mistaken for desperation, and should I mention that my past summer job has offered to keep me on next year and that I have an upcoming CB at big law, or should I wait until the CB at this firm to mention that I have other options?

My two (potentially worthless) cents: I think it's just a matter of how you say what you know you want to say. First, don't force it awkwardly into a non-relevant part of the interview (e.g., a question about some school activity), and second, say your piece confidently but calmly. Don't get all giddy or over the top: just methodically explain your reasoning.