Dear ... 
I want to thank you very much for interviewing me for the __(type of position)__ position in your firm.  My education has well equipped me for this job and I believe that this, along with my sense of enthusiasm, will be what it takes to ensure my success. 
You expressed some concern in our meeting, that I do not have practical work experience in the area of __(type of field)__, but I believe that my education plus my willingness to learn and ability to easily obtain new skills, equips me well for this role.  I am convinced that I can do a good job for you and I promise you I will not let you down if you give me the chance to show what I can do. 
I worked my way through college which shows a strong work ethic and determination; qualities you said were important to success of your company.  I am very excited about this position and I hope than you can believe in me as much as I do. 
Again, thank you for the time you took to meet with me and the inspiration you gave me in launching my career. 
Sincerely,