What is it?
Observation is a process of watching and listening carefully to users in their real context during their natural activity.
How can I use it?
Minimize your interaction and leading to observee. Document the behavior, events and activities of the person. Not your comments and ideas.
When can I use it?
You can use it to understand an ongoing process or situation especiall other data collection methods, such as surveys, questionnaires, et., are not effective.