Carry out enough research on your subject to feel sure that you have a good insight into him. Try to avoid getting too bogged down in other people's opinions, though, as this might be detrimental to your own viewpoint. Establish a good rapport with your subject. Take a clear set of questions with you, but let this be your guide, rather than your master. Do not stick rigidly to any set of questions. Ask if you can record the interview, as this will keep you from having to frantically write or type everything the subject says.
Include narrative in your profile. Avoid a question and answer format. Weave questions and answers into your piece, but try to keep your authorial voice out of the piece, as this is distracting to the reader.
Include references to the subject's appearance, dress and mannerisms, without being offensive, or dwelling on any of these characteristics. Instead, include them in a way that paints a word picture of the subject. If a family member comes into the room during the interview, or is mentioned, weave this into your profile, as this can show yet another aspect of your subject.