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I guess I'll answer your question by saying that when I plan a shoot well, it always results in better photos. Usually, the most solid location finding tool is to look for public lands, especially National Parks, State Parks, Bureau of Land Management Lands, National Forests, Wilderness Areas etc. Basically most places where hiking, camping, and other outdoor activities are encouraged. Some places are closed at night and private property is just a no-no, so it's usually a safe bet when the place has been designated as a camping area.
Some of my favorite spots have been on Bureau of Land Management areas. Many are designated OHV (Off Highway Vehicle) areas and others are just empty areas that aren't suitable to call National Forest land but many like Alabama Hills, California and Trona Pinnacles, California are downright beautiful and often not very crowded (at least compared to, say, Yosemite).
I'll often pick the places to try and make sure that they're in relatively dark sky areas my current favorite resource for this is Dark Site Finder. Pick times between the last and first quarter of the moon. If the moon is more than 50% illuminated, I'll usually not plan for that week.
From there, I'll usually try to find places where camping is allowed and build my trip around being able to stay at least one full night. I sometimes make trips that don't last the whole night, but it's always a lot better when you don't have to drive home tired.
Final scouting and planning is usually done on-site. I'll use Stellarium to understand the time and direction where the Milky Way will be visible. There are also other software tools I use too: PhotoPills for iOS and PlanIt! for Android are both great apps that help with planning.
I'll visit the place I want to shoot during the daytime and use these apps to anticipate my compositions. Once I'm satisfied with my choice of actual shooting locations, I usually stay there and wait through sunset and dusk. Being there in the light, before it gets dark helps on two fronts: It allows me to pre-compose shots in nice "magic hour" light (yes, I take daytime photos too!) and it also allows me to gain familiarity with the area. Places can be scary at night and being familiar with it in the light really helps with the psychological side of being out in a new place in the dark.
Altogether, it can take me anywhere from a day to a few weeks to really decide where to go. From there, it can be up to two weeks more to wait for the moon cycle. I rarely plan a shoot more than a month in advance but that's just me. Working for myself has a few benefits.
there is an app for Android named PlanIt!. It might be what you need