When you get to use a turret gun in certain parts of a level, click Left Analog-stick to zoom in 3x. This will help you see what you are shooting at, and result in better aim.

During the opening screens, press L and R to zoom in the image in the background.

On most weapons, you can zoom in by 3x pressing R.

Another way to zoom in is to click the Left Analog-stick up to three times.
While zoomed in, aim for the neck of most enemies and their heads will pop off. Each head is worth Skynet Tech points.

Finish all the training missions under the time limit, then press L at the mission complete screen to see what you have unlocked.

Aim for a terminator's head while in battle. If you shoot its head, it will pop off, and you will get a lot of Skynet Tech points. Sometimes when you shoot its head off, it will run around shooting its gun in the air and then explode.

Conserved Adrenaline Attack
This can be done with the baton weapon - just before you "fire" the baton (i.e., attack with it), turn on the adrenaline and press fire. Once the animation starts, turn off the adrenaline to save it. However, if you continue to hold down fire, you'll notice the baton attack is "powered up".