Be specific about the candidate’s qualifications and successes. Describe what the person has done using specific instances and examples, rather than generalities. Whenever possible, give evidence or stories to back yourself up.
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.