There always seems to be something in a previous walk that triggers an idea. Early on in my latterday walking I made a rule not to return immediately to the last walk done area. I seem to have had 3 areas of interest going on in my head at any one time.
What are the reasons for wanting to create a route;
My partner may express a wish to walk by water or in trees, so quality of way with a specific interest may be the focus.
If curiosity is the focal reason then it might be a destination or a feature, these often emerge from a distant view on previous walk.
Then there is the X zone, the area that is forbidden ground, what lies within? This so often can be paired with information gained from speaking to locals.
So many little triggers that get me looking at the map, seamless MM as mentioned by VGH, I must get a larger moniter, 3D view so often creates that additional little gem of intrigue, and try to use the National Library of Scotland's seamless OS alongside on a small moniter is very restrictive.
I have been frustrated over the years that the idea of 'Walk Design' has repeated failed to draw support both on this forum and others. The lack of criticism of routes published has left the sport with an unfulfilled armoury of information to use against the smug arguments of the occupiers of our countryside.