In 'Fuel Spots' I explained how to get in the window by the white 'Compy Corp' tanks via forklift. Here is an easier way: Go inside that building and face the tanks. Jump on the left end of the conveyor (flat platform?) and jump left on to a barrel. Turn around and jump onto a higher (brownish?) platform, jump rightish to the metal part that sticks out the furthest from between the tanks, jump onto the pipe that come out of the right tank. Then jump right to the window or left to the dark corner.

(SnD defender spawn); One of the spawns is between 2 buildings with an army truck right behind you. Starting there, go into the building on the right, go upstairs and look out of the window that overlooks a low cement wall and an explodable tank. Jump onto the wall (hard to do sometimes), jump onto the tank, jump through that window above you. Normally, it is much easier to just run up the stairs of that building, but this route is nice for suprising enemies camping up there who would be watching the stairs.