I'm near the end of a long XC from upstate NY to South Dakota and back. The route of flight took me from NY-PA-OH-IN-IL-WI-MN-SD-NE-IO-IL and when I finish up in the next day or two IL-OH-PA-NY, for a total of about 4000 NM. Over the last six years, I've flown my plane fairly long distances (i.e., in excess of 500 NM) a couple of times each year.
I start out with a plan but the plan doesn't always survive the weather and last-minute decisions. I have many times been at an airport and decided where I was going next at the very last minute. Since I like to stop every 200-250 NM, planning the next leg is often pretty easy:
* What direction do I want to go in next?
* What airports are there in that direction around where I'd like to stop?
* What's the fuel price at the FBOs?
* If I'll be landing outside of normal business hours, do they have 24-hour self-serve fuel?
* If I'm ending for the day, is there lodging available? Someplace to eat? I'm a lifetime platinum Marriott member so I just call Marriott and ask if they have a hotel near where I want to stop but Foreflight will list a fair number of local options for both food and lodging, as will other resources.
* Are there excessive landing/tie-down fees? A quick call to the FBO is usually an excellent source of information.
* If the weather is forecast to decline in some horrific way, do they have available hangar space and, if so, what's the cost?
The first time I took the plane halfway across the country, this all seemed really, really complicated. Six years later, I don't stress over it at all. I pay very careful attention to the weather but the other stuff is pretty easy. I like having a general plan for where I'm going but leaving the details flexible. That's how adventures happen.