Before starting this game, be sure to set the Difficulty to Easy and Energy Level to Easy.
Mission 1 is straight forward, just try not to lose too much health. When you get to the shooting range section, look out for health packs and shoot them to collect.
Mission 2 is what you need to save your energy for, at the end, a tougher enemy shows up and I just spammed special attack on it to make defeating a lot easier. Special attack is defaulted to the Triangle button.
Trophy pops at the start of mission 3 provided you have not died (lost all of your health) at any time.