Dear …
I want to send this letter to you so that you know that one of the goals I have, is to become a __(name of position)__ with __(name of organization)__. I am currently working very hard towards that goal and have been seeing my results improving each month as I work towards that end. I know that I do not currently have practical work experience in the area of __(type of field)___, but all the same, I do believe I would prove to be a great candidate for that position.
With my existing experience, my education, my willingness to learn and my immense desire to take my career into a __(type of position – i.e. management)__ position, I believe that I have what it takes. My ability to easily obtain new skills, has served me well in the past and I believe it would help me to do well in this type of role too. I am convinced that I could do a good job for __(name of organization)__ as a __(type of position)__, particularly in the __name of community)__ community. If given the chance to prove myself, I can assure you that you would have my total commitment to __(making the branch/becoming/etc.)__ the biggest success possible!
Thank you for taking the time to consider me for a__(type of position)__ the next time one becomes available. And let me assure you that I will not let you down if you were to give me the chance to show what I can do.
Sincerely,