Drilling is one of the most popular techniques of site investigation. Its accuracy is fundamental to a successful site investigation program. The drilling supervisor should have a sound knowledge of construction methods and design process and be familiar with drilling techniques as well (e.g. their limitations and ways to interpretation). Unfortunately, in most cases, a junior engineer instead of a senior one is sent to the site as the supervisor. Therefore, it is highly possible that accurate and useful results of underground conditions may not be obtained. Based on the author's experiences on site investigation, checking lists concerning the scope and process of drilling are presented in this paper.