Easy way :-
The easiest way is to use the maps given in the forum. i can't remember which thread, try to look around. the map is in german. but u can probably understand it.(come on..

)
Hard way :-
finding these sets are tricky. but the scorpion set for me is the easiest set to find out of all those f. fortresses in the game. this is due to how the terrain is situated in the map. when you
look at the map there's the first large land with 6(or 5?) islands around it and the second large land where the general's fortress is located.
search these islands first. clockwise/ anticlockwise. some of these island have 3 levels of flying land. some have 2. so search all these level. i start from the bottom to top. to search for the set, always search if there is an entrance below the land morph into human there and WALK to the surface. dont just drop on its surface to avoid missing important camps where some sets might be situated. ( this goes for all flying fortress map that has sets ). after u have finished searching on 1 island mark it on the map. then move to the next.
after u finish the islands, start searching the large land at the center of these islands. from the bottom up. u must be thorough. after all this had been done will u move to next island where the general's fortress is. again search thoroughly form the bottom up. i assure u, if u search patiently like this, u won't miss it.