J.R.R Tolkien, "Not all who wander are lost", but if I wander without itinerary I might get lost and I loveeee making itinerary and can be said I am good in that, the complication of combine all the wishes and limited time we had was fun for me.
What you need when design an itinerary:
Especially on a road-trip, you need to be able to measure the distance and time consuming and of course the route, surely you don't want to make back and forth trips. With this you can easily through in you picked lists to fit the route, as well as time for spending in the place, whether you need a rest in between after a long drive.
Nowadays you hardly survive with this, surf and read a lot of information both from the tourism official site, TripAdvisor or travel blogs, so you will know pros and cons moreover plan to fit your budget. Mostly i go with travel blogs and the tourism site, keyword is very important, if you want to go on budget, click New Zealand on budget
For me working in excel sheet is the most efficient way to have all the details, I usually plan day by day with the ETA, ETD, opening hours, costs and details of necessary info or website to refer to.
The least but the most important, you gotta have time to do all these, I spend 2 days for New Zealand itinerary and amended it quite a few times before ending with the best one (of course the best I thought before actually do it), this is when reality hurts sometimes
Please find in my collections of Itinerary that I made prior to our trip. This is for guidance only how to plan but to actually do it most of the time I don't follow and in this trip, all the trip after Milford Sound were cut due to tiredness and probably disappointment after heavy rain stopped us for Milford Cruise, although blessing in disguise with snow in the land of Lake Tekapo. Check it out, our road trip just gets better with my day to day travel story