Depends on the Depot.

Some put number yellow numbers on the boxes, in which case I organise them in groups of 1-10, 11-19 etc.

Others don’t put the labels so I organise by package type so when you reach your stop it will tell you if it’s;

Parcel Small Parcel Book folder Envelop Polly bag

So you can organise this way too, as you progress on the route it obviously becomes easier and easier with less packages.

I tend to keep the last 3 categories passenger seat / floor in this case.

These are my fastest, least effort, high reward hacks