For the purpose of the trial, I'm trying to produce a bunch of different vehicles based on the same basic chassis (an APC) so the first job is to design the base chassis.
Step 1: a very basic geometry block out, mainly just to get the perspective right.
Step 2: draw/paint over the model in photoshop to add details
Step 3: use the drawing to refine the basic model, adding detail etc.
Step 4: pick an area and draw/paint more detail/options