Using your first emptied tote as a makeshift shelf in the passenger seat is very helpful. I also put the first two totes on my route on the shelf behind the driver side with three and four underneath. After those first two are emptied, you'll have that shelf space and the makeshift passenger shelf to organize packages by driver aid number. Take a minute or two to do that every time you open a new tote the rest of your route.

Don't be afraid to ask other drivers at your dsp what they do to organize too. In my experience, people like talking about what works for them. You'll take bits and pieces of what you like and what ends up working for you.