You need to find most by playing a Map again and again.
Even then it is a matter of taste.
Fall of Tobruk/Axis (at later stages/Cap-Points positive to avoid flanking)
Between Aussie Main wooden stairs and the large Tanks at Harbour Outskirts
you'll see two Ruins, chose the one on the right side if facing Aussie Main from Harbour.
Crouch inside, then you can enter a part of the ruin compartment under comfortable floors.
This is a vital position that will free you from heavy Barrage as expected in the closer compound to
that main. The Mortar shells halfway to Harbour and the Hotel area, see this estimated
Map, as well a screenshot showing this position. I use to have a good sight even to the front,
thanks to a door opening where you can trace them walking for you.
If you ran out of Ammo, Harbour Cap Point is the best choice, just watch for Hostiles, Bullets.
You can easilly re-enter that Spot then.