I have tons of kickass goals that I look forward to experiencing in my future lucid dreams. 
However! 
one thing that I’ve always felt unsure of is… just exactly how specific should I be when I prepare for them?
I mean, goals’re nice and everything, but if I just think of my goals when I fall asleep then it might just turn into an ordinary ND.
Yeah I might dream about the experience, but not actually turning lucid.
So how exactly do you trigger that lucidity part when you think about that planned experience?
Is it enough to just vividly imagine the goal itself and feel excited about it, or should I prepare an exact location, a certain attitude etc?
Well it depends. I guess better preparation would result in better results. But it doesn’t have to be. Even though you make a great preparation before bed time it really depends on how lucid you are in your dream.
If you are low lucid then you might not even remember your goal or you will do something like on automatic mode. If you have high level lucid dream then things like good preparation might come in handy. So yes I would suggest the best possible preparation in order to remember the goal once you are lucid.
How your “good preparation” will look like is completely on you. You can imagine details or you can even write them down(this I find very good method), if you can draw even better. Take time to plan out your goals. If you make time and if you take time then your subconscious mind will see that as important and with time those will sink in.
Also good thing is when you do plan your goals you can meditate a little bit and actually think about your goals…
Good luck! 