I'd be happy to be your reference but, in order to give you the best possible reference, you should come and chat with me about the position you are applying for.
Also, please send me the following information (the more information I've the better I can answer potential questions about you in relationship to the position you are applying for).
This is important to help me figure out the type of position you are applying for.
A link to or a copy of the job posting
A link to a website with more information about the group/program/university/company you are applying to.
This is important to help me make may answer to question more personal.
Please provide me with the following information:
Your current CV/resume
All the material that you have prepared for your application, especially your cover letter and your personal statement.
Two or three paragraphs written in third person where you describe yourself in relation to the position you are applying to. What is that makes you the best candidate for this job/group/school?
If you have specific courses or extra curricular activities that you think are relevant for the specific application, add them to the document above