Hi, Is,
nothing fancy yet, basically doing some mapping.
I have a basic mapping layout for each project, then I use some suitable skin to have an idea of what will be the resolution of the texture with this layout I made, and have a feeling for the kind of detail it will show. I'm trying to be consistent so planes of the similar size have similar detail.
Then I move a suitable part of the texture, over the surface of the model, to some area that needs some care and atention. And try to fix the issues of that area.
After some test, skins have proved to be the best tool for this, so I choose some with good panel lines and rivets that will help as a guide. This is to avoid finding this kind of problems later on, when already working on the skin, as they are more annoying or difficult to fix. This way you can even change the 3d in advance to make things easier or overcome some mapping issues.
Some examples with a Phas3e skin (an He 111 here) of his last Random Crap pack (thank you so much, Phas3e) to check resolution and detail:

Wheel spats, a difficult area due to his curved shape, that needs some tweaking as planar mapping doesn't work too well. Instead of going straight, lines should follow the curvature of the spat :

And after fixing the mapping, (now lines follow the shape of the part but still they are paralel and perpendicular):
