This skill builds upon the skill "Picking a point in the distance towards which you want to run". In and of itself it is very simple but it is something worth consciously thinking about until it becomes second nature. Once it becomes an ingrained habit you should find that you are able to run through the forest more efficiently and get caught in thick vegetation less often. This is part of what is commonly refered to as "micro-routechoice".
To run effeciently through the terrain you should be looking up into the distance and picking a visual point that you are running towards (based on what you read on the map and / or a compass bearing). Once you've picked that point you should look at the terrain and look for the areas that are most runnable. By picking out these sections of the woods (or other terrain) you can deviate from the straight line to be able to run through the most open sections of the woods as much as possible.
No relevant resources have been linked to the skill or practice "Looking ahead and seeing what areas of the forest are most runnable".