You will have asked the permission to include the names of your references before including them on the list. If it possible you should advise the people on the list about the details of the position that you are applying for and what skills and experiences that are necessary or preferred for the job. This may not always be possible if you are applying for several jobs at once but it is far easier for your reference to write a letter of reference for you if they have this information.
When I am asked to write a letter of reference I always ask for the details of the position, particularly the requirements of the job. If I know for example that the job requires specific tasks such as greeting the public or writing reports then I know what to include in the letter of reference. Even though the person may not have direct experience with the tasks required in the position, I can describe why I think this person would be successful in those tasks because of other skills or experiences they have. For example, if I am writing a letter of reference for a student that I have worked with for a position that requires report writing, I can outline the skills that the student has demonstrated in school.
Clearly, an influential letter of reference outlines the candidate’s skills that apply directly to the position.