Lost circulation is a billion-dollar problem well known to the petroleum industry. During the previous decades, different approaches and remedies have been developed with limited success. To classify lost circulation issues in a comprehensive way, severities, mechanisms, special cases and special concerns are characterised in the beginning of the thesis. Additionally, a step-by-step summary of how to effectively diagnose lost circulation is introduced. Depending on the loss scenario, a corresponding cure must be found. Available lost circulation material (LCM) and settable material are categorised and specified. This is carried out with the help of available product lines of manufacturers. Subsequently, the treatment options are discussed based on loss mechanism and severity to see which treatment must be applied under certain circumstances. Ideally, the latter is scientifically proven. Currently, most lost circulation material testing apparatuses are akin to the American Petroleum Institute (API) design and therefore function like filter presses. An improved dynamic test stand design is created and discussed to comparable evaluate LCM and settable material under certain conditions. The test stand design is rotatable, can simulate different fracture angles and sizes while various flow rates and temperatures can be applied. Five wells from TAG Oil Ltd. New Zealand most prone to lost circulation confirm the recommended selection of LCM and settable material by showing what was done and what could have been done to combat lost circulation more effectively. Several lost circulation decision trees of various companies and their limitations are assessed in this thesis. Consequently, an extensive evaluation matrix is created. Possible loss scenarios characterised by mechanism, loss rate, inclination and reservoir vs. non-reservoir are matched to available treatment options and recommendations result. The matrix is intended to be a first-action-tool when losses happen and give rapid guidance to the available options. Non-productive time (NPT) can be minimised and best possible actions can be taken.