It would be interesting to hear other architects here opine on how they think the design process is initiated. As the famous song from “Sound of Music” says “Let’s start at the very beginning. A very good place to start” 
I personally believe that there are no real fixed starting method by which a design really starts.
Once, I even started a design by arranging window openings suspended in thin air in the model in TAD! Let me explain: I was given a commission to do a hotel resort at the hill-station of Devikulam, which is a hamlet situated higher than the resort of Munnar in Kerala. My client had taken me there; and after a road ravel on lot of winding roads we reached this heavenly place (“Devikulam” indeed does mean lake of the goddess)
It was quite cold, with a beautiful mystifying fog all around. We were near the mountain tops of the Sahyadiri mountain range on the west coast of India. We could not be around that site for more than a few hours.
I knew it would be difficult for me to revisit that place again. I had to think fast. I knew that the wonderful views of the scenery around the plot would play a crucial role in the upcoming design. But frankly, I had no clue what were the requirements: The client had not yet decided anything much.
So I stood there like a movie director and started framing views – first with my fingers; much the same way a movie director would. Then I started imagining “What if there was a window right here? That would capture that particular mountain peak” … I took out my laptop; and the first “objects” to appear in the plot of land modeled inside TAD for that project were these window openings.
When I returned, I had this model with a lot of these window-openings suspended in thin air in the model – with no walls, spaces … in fact nothing else!
So that was surely a very unusual way to start work on a design.
Unfortunately, the client later on got into some entanglements and the project never materialized. Sadly, my office also ended up deleting that particular (and only one) TAD file I had made – someone thought that since the project is no longer viable, let’s remove the folder!
It would be nice to hear how others went about starting their design projects. AIM does talk about information requirements right from very early stages of designing. So the starting point surely is crucial!