Whether you're pursuing a new job, educational opportunity or even a scholarship, a letter of recommendation usually comes in handy. But if you're unsure who to ask or how to ask them, getting that little letter can be very tricky.
Think about who has positive things to say about you first. Not all of your professors or employers will have positive views of you and it's hard to tell sometimes. To make things easier, choose a person or two who have mentored you and know you very well. Trust is also important as you want them to portray you in a positive light.
Do not choose your current supervisor unless you two have discussed specific plans for position changes. However, if you're pursuing growth in education or for an award, asking your supervisor is perfectly acceptable.
Call or email who you'd like to write the letter. Tell them first what you're pursuing and why you would specifically ask for him or her to write it. Make sure your points are compelling.
Decide if you want the letter to be general, giving it the ability to be used for multiple purposes over the next year or two. Having a multi-purpose recommendation letter, especially in the professional field, is always useful because it saves time later.
Offer to write the letter yourself while asking, giving them the ability to edit it to their liking. Make sure to clarify this as respecting their time instead of distrust of the person's opinion of you. Also make sure that you give the person you're asking a two-week notice to write the letter.
Ask if you can receive a copy of the letter after the fact for future references. If the letter will be emailed, ask to be CC'd on the email.
Thank the person for writing the letter by sending a hand-written note, calling or sending an email to the person.
Remember to ask for a letter of recommendation in enough time for the person to write it. Two weeks is standard, but a month in advance couldn't hurt either as long as they are sent a reminder a week before it's due. Also be sure that you've known the recommender for a good amount of time before asking them.