For good tips on targeted, effective thank-yous, take a look at Mastering the Art (and Science) of Thank-You Letters by Laura Labovich at http://www.careerealism.com/mastering-art-science-thankyou-letters/
And use the tips immediately after the interview while the discussion is still fresh in your mind. From personal experience, I can give examples of thank-you letters that made a difference. One young lady sent a thank-you note to the Dean of a College after an information interview and was awarded an extra $2,000 in scholarship money for her studies. Another job seeker sent a thank-you after meeting with an interview panel, and his efforts were so appreciated and targeted to the job that he became the candidate of choice.