Once your hero knows what he wants (his desire) and knows what challenges he's up against (his opponent), he needs to formulate a plan that will help him to get the desire.
This plan can be highly detailed. In Alan Moore's graphic novel Watchmen, the character Ozymandias explains his plan in full towards the end of the story, even pointing out this plot element when he says, "Dan, I'm not a Republic serial villain. Do you seriously think I'd explain my masterstroke if there remained the slightest chance of you affecting the outcome?" You also find intricately developed plans in robbery tales like Ocean's Eleven or The Thomas Crown Affair.
At the opposite end of the spectrum is a very vague plan. In Full Metal Jacket, Joker's plan is very vague. In fact, broadly speaking, he doesn't have one other than to follow the orders given to him by the chain of command. He's a low-ranking Marine, a private in the first half and a corporal in the second. This isn't bad storytelling at all, but acceptance of reality. If Joker were a general instead, then he'd have room to plan because he would have the authority to do so.
Throughout Full Metal Jacket, Joker's only plan, mingled with his desire, is to survive. I think subconsciously, he trusts Hartman's tough curriculum in boot camp because he knows the whole point of boot camp is to prepare trainees for combat. If he goes through the paces, he should come out okay, and he does; he makes it through to the end of training. What differentiates Joker's plan in the second half is that he now has those skills to get him through the ordeal of the Battle of Hue.
Psychologically, I don't think Joker has any plan at all for his mental survival. In boot camp, he's broken down and reassembled as a Marine. Then, in Hue, he's giving priority to his physical survival over his mental survival because there's no point in trying to get your psyche to cope if your body's dead.