Define your focus and objectives when you first meet with your observer.
The observation checklist is divided into six sections related to general teaching areas, plus three sections related to specific teaching situations.
If your observed session is to be a lecture or a tutorial/workshop you may only want to select items from the general sections.
If your session is to be one of the specific teaching situations (clinical teaching, laboratory/practical session or a PBL/CBL) you may want to select from the points which are specific to that style of teaching and/or some of the general points.
The choice of items will be guided by the objectives of the observation and the particular aspects of your teaching that you would like feedback on. You can choose the items in collaboration with your observer or select them yourself.