We strongly recommend the use of a formal resignation letter.  It gives you a chance to clearly communicate your intentions as well as a way to express your thanks for the opportunities and experience you received in your current position and move on with class. 

A Good Resignation Letter Should Include the Following:

1. Focus on your enthusiasm for your new position, rather than why you are resigning. Giving your employer the reasons that motivated your search for a new job is an invitation for your employer to try and fix them. If they have not fixed the problems you've had in their environment before, there is no reason to believe there will be a permanent fix in the future.
    

2. Thank your employer for the experience you've gained in his/her employ. Let them know that you have weighed your options very thoughtfully and ask them to honor your decision to resign.
    

3. Don't burn any bridges! You won't change them, and it won't help you. If you can't thank them for your experience there, just stay with the facts.