IWTL how to properly plan for an epic trip in about two years.

Just got it in my head what I want to do for my 30th Birthday which is in just under 2 years. I want to do a trip to South America and have a rough itinerary in mind but I need help in hammering out the details.

I've honestly been terrible at planning trips because I always tend to just go with the flow but this will take a lot more planning as it will cover about 3 countries, likely cover a lot of ground, and be dependent on very specific dates.

What are the best tips to make sure I do this right?