Chose a comfortable setting to talk the student. Avoid having the discussion around the student's peers as students are often shy and nervous about revealing their feelings around their friends. Individual attention may work best.
Start a general conversation. Ask how she is and if she's having any problems. These questions may reveal strengths and weaknesses on their own.
Ask the student where he excells. Have him elaborate on this skill. Ask detailed questions. Take notes as the student speaks, but maintain eye contact to avoid alarming him. Move to a tangential subject or skill after the student has described the first thing at which he excells. For example, if the student says he likes computers, ask him about specific software.
Ask her about what she thinks she could improve. Avoid overtly criticizing her. Instead, prompt her for self-criticism. Take notes. These criticisms will often be weaknesses.