A major source of beginning to understand tactics is dealt with by Toplevel sailing as tactics for the first half of the beat (when the boats are diverging into a wider area, as against tactics when the boats are converging into the tiny area around the mark.
During a racing beat there are some fundamental differences between different phases of the leg, this mean our decisions and priorities as racers should be different between different parts of the course
The movement of water over a course area is rarely uniform. Because of this factor the racing sailor has to have an understanding of where currents are at their maximum, how this helps or obstructs progress and where a current will take you sideways away from the mark, or sideways towards the mark. Where possible, using current in different areas to enhance the speed around the course can be much more rewarding than finding a lot of boat speed through increased wind speed.