when I am just aimlessly doodling, I tend to just draw random things, upon which I build, as each idea inspires a new thought, as below:
or sometimes I have several unrelated images filling a page, which I may try to connect by creating a unifying landscape tying them together, as with this scribble from the back cover of an old notebook from school (spanish class, I think):
more examples of progressively-random doodles:
