Prohibited: firearms, ammunition, controlled knives, drugs, obscene materials, items endangering national security, dead animals, and plants/animal products from epidemic areas.
Restricted: fresh fruit, meat and dairy are usually barred; cooked and packaged food depends on the case; seeds, soil and pets need declaration and quarantine.
Medicine: personal prescription medicine should carry the prescription and original packaging; narcotic ingredients (some cough syrups, sleeping pills) need special declaration or may be treated as smuggling.
E-cigarettes: personal use is allowed but selling is not; large batteries and drones must be declared, and drones are restricted in some areas.
Cash: up to USD 5,000 equivalent needs no declaration; above that, declare.
Reminder: when unsure, use the red channel and ask customs; banned items may be confiscated, and serious cases bring fines or visa trouble.