An easy way to take over territories is to find a high place like a roof top. First, kill a few gang members to start the war, then get onto a roof. When you are up there, they will still shoot at you, but will not have accurate aim and will miss frequently. It is recommended that the "Air Strip" missions be completed first. To easily take over territories, go to the airstrip and take the Jetpack. Go to any enemy territory and start a gang war by killing some enemy gang members. Fly and land on any building roof you can easily see incoming enemy gang members. Kill all gang members from up there. By doing this, you can easily hold all enemy territories. Be patient when killing gang members, and try to stay inside the war zone. The distance between the airstrip and enemy territories is long, but this is the easiest way to quickly and safely hold enemy gang territories. All territories can be held by using the Jetpack, but only one by one.