Every process is different for each piece, but I will try and answer your question. Usually it starts off with a basic idea ("I want to draw x"), but most of the pieces I end up creating are so far from what the original idea was, that I am tempted to say that they just "happen". Or rather, the thoughts behind them happen while I draw.
With this one for example, I started off with the bunny, and then suddenly had the idea of making it into a question mark as I was adding to him. After that, the details, like the globe doing both a rude gesture and one for peace just kinda fit in with the idea of the question mark and the concept of "Indecisive" and/or confused. I guess it's how I felt at the time, and sometimes still do. It's hard to know what to think in life as things are not always black and white.