I agree with amplified - but the reality is that some of the profs/supervisors write so many of these things that you might be better of really writing the letter for them, but do it this way, set up an appointment, take them to lunch with the sole purpose of having them discuss you and to collaborate on the letter, but then you write it for them - that way their voice and thoughts can come through.If they are willing to write a letter, give them as much support as possible that is tailored to you and them - don't just print out a page from some website, take the time to write to them using the information you have gathered. The more you put effort into supporting them in this endeavor, the more you will get from them or at least from the ones who are most worth asking.
Here is a suggested items and an outline that I pulled from a few sources, including some law school sites and Ivey's book:
Law schools are looking for information that discusses an applicant’s specific qualifications and accomplishments. The most effective letters are written with candor, detail, and objectivity about your achievements and potential to succeed in their law school.
Questions that can help frame the recommendation:
1.Relationship, past and present.
2.Comments on analytical and expressive abilities, study/work habits, and/or personal motivation.
3.What special interests, personal qualities or background distinguish you from others?
4.What observations do they have of your character and integrity?
5.Relevant insights they can offer about you that are not likely to be available from other sources.
6.How do you compare with other promising contemporaries?
7.Can they evaluate your academic promise in a rigorous professional program?
8.What was the nature of any work you have collaborated on, can they evaluate the quality of the work/collaborative abilities.
9.Comments on any contributions you have made to the community you have in common/how you have made a difference.
Of course the recommender's personal style will be the strongest influencer as to what you include, but here is a common format for these letters:
•Express pleasure at having the opportunity to recommend you.
•Indicate how long and in what capacities they have known you.
•Let them know that they do not hesitate to recommend you for law school. Then explain why – elaborating from items in points 2, 3 and/or 4,5,6 from above.
•Explore one or two experiences you have shared, perhaps even comparing you to others in a way that makes you stand out from the crowd – creating a standard for comparison in some way. This uses items from 6,7,8,9
•Finish with information on how they may contact the recommender if they need to clarify anything or require additional information.
Helpful details that may or may not be obvious:
•Begin the letter of recommendation with ”Dear Law School Admissions Committee.”
•If they have letterhead, use it, Law schools like the letters on letterhead,some actually require it.
•Oh, and make sure they sign the letter – apparently Law Services gets a lot of unsigned letters that they have to send back. (duh)