The person you ask should be able to speak about both your academic ability as well as character.
It's important to provide your referee with the reference letter request form, and have a discussion about what the reference letter is for. I suggest attaching your resume along with the request form so they can speak to all of your accomplishments.   

recommendation letter template / format 
Your Contact Information 
Your Name 
Your Title 
School Name 
Address 
City 
Postal Code 
Date 
 
Salutation 
If you are writing a personal letter of reference, include a salutation (Dear Mr. Johnson, Dear Dr. Jameson, etc.). If you are writing a general letter, use "To Whom it May Concern” or don't include a salutation. If you don't include a salutation, start your letter with the first paragraph. 
First Paragraph 
The first paragraph of a recommendation letter explains your connection to the person you are recommending, including how you know them, and why you are qualified to recommend the person for employment or school. 
Second Paragraph 
The second paragraph of a recommendation letter contains information about the individual you are writing about, including why they are qualified, what they can contribute, and why you are recommending them. If necessary, use more than one paragraph to provide details. 
Third Paragraph 
When writing a letter recommending a student for a specific scholarship or post-secondary program, the recommendation letter should include information on how the person's skills match the position they are applying for. 
Summary 
This section of the recommendation later contains a brief summary of why are you are recommending the person. Use phrases like "strongly recommend", or "recommend without reservation" or " Candidate has my highest recommendation" to reinforce your endorsement. 
Conclusion 
The concluding paragraph of your recommendation letter contains an offer to provide more information. Include a phone number within the paragraph, and include the phone number and email address in the return address section of your letter, or in your signature. 
Example: “Please feel free to contact me at 123-456-7890 if you need any additional information or clarification.” 
 
Closing 
Sincerely, 
Recommender Name 
Title