When in the field your position is vital, the cover that is provided by the landscape can work in your favor or cause nasty situations. Some cover will help you to block visual contact and some protects you from gunfire.
To be and remain unnoticed it is important to know the position of all your target and other hostiles to avoid suprises. One of these suprises is getting into an ambush or run into a hostile unexpected. If you know where all the pawns are you can manouvre accordingly avoiding unnecessary contact.
Another thing to keep in mind is not getting cornered by cover, it is better to have no cover from the back then to get boxed in when things go wrong. Don't get me wrong, if nothing can come from the back it is perfect, but be sure to have a fallback plan.