LegalJob has recently talked with folks leaving their current job for something better.  Two items to consider when leaving:

1. It is not you, it’s me — Everyone knows not to burn bridges when leaving your current employer.  LegalJob suggests you go one step further and take a bit more affirmative action when leaving.  Communicate with your superiors that the reasons why you are leaving have nothing to do with deficiencies of the firm but everything to do with your current preferences which may have changed over time (i.e., location, lifestyle, type of work, etc.).  Your preference list should be items that the current place cannot readily change so there are no hard feelings (so not because of the jerk factor, for example).  You never know when you could be dealing with the same people again.
2. Secure a recommendation letter — This advice may seem a bit counterintuitive.  Why does one need a recommendation letter if they have already secured the next job?  The recommendation letter documents your strengths and accomplishments while memories are fresh (your memory and your superiors’ memories).  Also, you will probably have the chance to contribute to the contents so the letter is an opportunity for you to emphasize areas of strength that are consistent with the niche you are starting to develop (or one that you would like to develop).  The letter also demonstrates that your reason for leaving was your choice and not because of your poor performance.  In addition, this letter is helpful to have in combination with the resume when interviewing in the future, especially if you tend to move around a lot.