{aspiring_to_clarity},
I've tried a lot of different approaches to journaling over the past fifteen years, and I can tell you that this can -- and maybe should -- evolve and change over time.
Sometimes just writing your thoughts and experiences can be more beneficial than any sort of system. I've also had more formal systems be very effective at some times. (See
The Birth and Death of a Personal Growth Practice | Manifest Revolution.)
I think the best thing you can do is to start by just putting your thought process (for decisions) and self-reflection (for goals) into written words for a while and pay attention to what patterns emerge. Make sure to include your mental and emotional responses to the outcomes of those decisions and goals later on. If nothing else, you'll increase your self-awareness and embed those intentions into your thought patterns, and that alone will be beneficial.
Good luck,
Andy