Dear …
  RE:  Request Permission to Attend __(Name of Seminar/Conference)__
Please accept this letter as my formal request to attend the __(Name of Seminar/Conference)__.  One of the primary reasons I wish to attend this __(seminar/conference)__ is due to the type of __(training/education)__ it will afford.  As an employee, my ambition is to be able to add more value to __(Name of Organization)__ by increasing my knowledge and skill levels and I believe that what I would take away from this __(seminar/conference)__, would help me to become a more productive employee. 
I’m quite certain that my attendance at this __(seminar/conference)__ will prove to be beneficial both to __(Name of Organization)__ and to me in that the __(specific type of education/training)__ will heighten my ability to __(briefly describe how you will apply it to your job)__.  In addition, learning __(about/to)__  __(type of knowledge/skill)__ will provide me with the means to __(briefly describe what it will allow you to do on the job)__. 
During my employment with __(Name of Organization)__ so far, I think that I’ve proven to be a responsible employee with good work ethics.  That is because my goal is to constantly grow as an individual and strive to become __(more proficient at my job/a better __type of position__/etc.)__.  In order to do this, I know that I must actively pursue new skills through training and education opportunities.  I see attending this __(seminar/conference)__ as one of those opportunities. 
__(Attached/Enclosed)__ you will find particulars on the  __(Name of Seminar/Conference)__.  I thank you for considering my request to attend and will remain hopeful of your response. 
Respectfully yours,