The purpose of the aseptic technique

The purpose of the aseptic technique is to control the conditions of the work environment so that sterile media remain that way until inoculated deliberately by the lab worker (you). The two tubes represent the "before" and “after" results when this is accomplished — a sterile medium is inoculated and grows to produce a pure culture of the unknown organism. List three precautions taken in the wet lab to reduce accidental and unwanted inoculation (also known as “contamination") of sterile media.