(1) Determine things about yourself that you would like a judge to know about you that you aren't or can't include in your application. This is where you should discuss your personality and how enjoyable it is to work with you.
(2) Cite to anecdotes about work you've done for the lawyer and how it demonstrates certain skills or traits about you.
(3) Provide comparative analysis of you as a lawyer/law student. ("She was the best
summer clerk that I have had the pleasure of working with." "I have worked with several law students from Harvard and he is the best.")
(4) Change your writing style. Even though the partner asked for a draft, submit a polished version. You never know if the partner will just use your "draft" as is. Therefore, you want to make sure you change the writing style so it doesn't sound like you.
(5) Keep it short and direct. An effective LOR points out why you are the strongest candidate, the writer is unequivocal with his or her endorsement of you, and helps humanize you. At the end of the day, the judge wants to hire someone who he or she would want to work with in chambers.
If there are certain endorsements or comparisons you feel uncomfortable with, just tell the partner that you are including things that a judge is looking for. Also, try using Google to find sample LORs. You should be able to find good examples and phrases to add to your LOR.