Exploration of the game world | Combat Middle-earth: SoM Guide
Last update: 11 May 2016
Middle Earth: The Shadow of Mordor is an open-world game and you can start the exploration of the first area (of the two available ones) (Udun valley) right after you complete the short prologue.
I recommend that you explore each area with utmost care, because many of the locations are being guarded by lots of monsters. Therefore, I recommend that you go on a reconnaissance, before you enter each new area. Here, you can use the Wraith mode, which highlights the enemies in the area, among others. The exploration itself is what I recommend because, between the main missions, you can take some time to complete side missions, to find collectibles or to interrogate the orcs that hold information on the members of Sauron's army.
What holds a special place on the world map are orc fortresses, because the abovementioned monsters stay there in large quantities. It is best to start visiting fortresses only after Talion becomes stronger. While in a fortress, try to stay in shadows. If, in spite of that, you are detected, try to get the monster that spotted you, as quickly as possible, before he manages to raise the alarm, because reinforcements will arrive in the fortress, otherwise, and things will get even more complicated.