Get feedback. If you’re not sure of your letter-writing skills, or if your letter will carry a great deal of weight for the candidate’s application, ask for feedback from a trusted colleague who may also know the candidate. If you are putting your reputation on the line for this person, you want to put your best foot forward with this letter.
Keep your writing action-oriented. Begin each paragraph with a punchy, active affirmation of the candidate’s qualities or character. Strong verbs are your friend.