In order to use american tactics you will require;
1. Medical Pods
2. Chopper Strike
3. Ammo Supply(Optional but makes AMERICAN TACTICS more effective)

In the beginning your Marines will be too poor to afford the helicopter building and ammo depo, so we must adapt, this is what the medi pods are for. In many of the campagin maps you will have enough build points to make 3 shotguners and give them a medi pod. After this just rush in to the nearest hive and rocket/blast to bits and get those sweet points.

Step 1. Position Helicopter Deployment Center in easily defensible tactical area
Step 2(optional) Position Tactical Ammunition Supply Depot in easily defensible tactical area
Step 3. Proceed to bomb the ever loving sh*t out of the alien scum then steal their land with your proud marines.