Bottom layer: things you will not touch until arrival
Heavier, bulkier items that stay zipped the entire flight belong at the bottom, both for weight distribution in the bag and because digging past them mid-flight is the most common cause of carry-on chaos.
Middle layer: in-flight needs
A layer with a light jacket, a book, headphones, and anything you might want without opening the overhead bin keeps the bag functional as a seat-side resource instead of a sealed box.
Top layer and outer pockets: security and immediate access
Documents, liquids bag, electronics, and anything you will need to pull out at a security checkpoint or gate check belong on top or in external pockets, so nothing else has to come out to reach them.
Questions people ask
Should liquids go in the main bag or a separate pouch?
A separate, easily accessible pouch near the top makes the security screening step much faster than digging through a packed main compartment.
Is it worth packing a change of clothes in a carry-on?
For any itinerary with a tight connection or checked bag, yes — it is one of the most useful things to have on hand if luggage is delayed.