To "steer up or to steer down" is the most crucial question for all geosteering specialists. In this first ever comprehensive technical guide, this question can be answered as the author takes the reader through the geosteering decision-making process. Focusing on three main sections: planning horizontal wells, geosteering methods; and steering instructions, the guide presents the complexities of geosteering in clear and simple terms, allowing the next generation of operations and wellsite geologist to learn the unique skill of geosteering horizontal wells in half the time.