paper and pencil – cheap, limited to writing speed
audio – good for think aloud, difficult to match with other protocols
video – accurate and realistic, needs special equipment, obtrusive
computer logging – automatic and unobtrusive, large amounts of data difficult to analyze
user notebooks – coarse and subjective, useful insights, good for longitudinal studies
Mixed use in practice.
audio/video transcription difficult and requires skill.
Some automatic support tools available