Eight weeks before

Check that every passport is valid six months past your return dateMany countries deny entry inside the six-month window, and airlines enforce it at check-in. Routine renewals can take 6–8 weeks — expedited costs extra and still takes weeks.
Check visa and entry requirements for every country on the itineraryIncluding layover countries — some require transit visas. Check your government's country pages, not the airline; e-visas and travel authorizations (ESTA, ETIAS-style) can take days to weeks.
Book a travel clinic visit for vaccinations if developing countrySome vaccines need multiple doses weeks apart, and proof of yellow fever vaccination is an entry requirement in parts of Africa and South America. Ask about malaria prophylaxis while you're there.
Verify each child's documents and consent paperwork if traveling with kidsChildren's passports expire in 5 years, not 10. A parent traveling without the other should carry a notarized consent letter — border agents do ask.
Check your destination's travel advisories and local lawsSome common medications (ADHD stimulants, codeine) are controlled or banned abroad; you may need a doctor's letter or advance permit.

Four weeks before

Sort out how your phone will work abroadOptions, cheapest first: local/travel eSIM, carrier international plan, roaming default. Confirm your phone is unlocked before betting on an eSIM.
Notify your bank and confirm your cards work abroadAsk about foreign transaction fees (often 3%) and confirm you have at least one Visa or Mastercard — Amex and Discover acceptance is thin in much of the world. Carry two cards on different networks.
Get a small amount of destination currency or plan your first ATM stopAirport exchange desks are the worst rate in the country. A bank ATM in the arrivals hall is almost always better.
Buy travel insurance that includes medical evacuation if long tripDomestic health insurance rarely covers you abroad, and an evacuation can run six figures. Buy soon after booking — some benefits require it.
Refill prescriptions to cover the whole trip plus a bufferKeep medications in original labeled containers in your carry-on. Insurers often need an override to fill early for travel — call ahead.
Enroll in your government's traveler registration programFor US travelers, STEP (Smart Traveler Enrollment Program) — the embassy can reach you in an emergency and you get alerts.
Book intercity transport and must-do activities that sell outTrains in Europe and Japan, and timed-entry sights, are cheaper and available further out.

Make two sets of copies of passport, visas, insurance, and itineraryOne paper set packed separately from the originals, one digital set in cloud storage you can reach from any device. Add card issuer phone numbers.
Check in for your flight and confirm passport details match the bookingName mismatches between ticket and passport can mean denied boarding — fix them with the airline now, not at the counter.
Arrange for mail, plants, pets, and an emergency house contactGive a neighbor or friend a key and your itinerary. Pause deliveries rather than letting them pile up visibly.
Prepay bills that come due mid-trip if long trip
Download offline maps, translation packs, and entertainmentDo it on home wifi. Google Translate and map apps both work offline if you download the country pack first.
Pack, with prescription meds and one change of clothes in the carry-onChecked bags misconnect on international itineraries more than domestic. Weigh the bag — international overweight fees are steep.
Pack plug adapters and a universal chargerCheck both plug shape and voltage; most phone chargers are dual voltage (100–240V), hair dryers usually are not.
Pack snacks, entertainment, and a spare outfit per child in the carry-on if traveling with kidsAlso confirm car seat and stroller gate-check rules with the airline.

Do the final house sweep: trash out, dishwasher run, thermostat set, doors lockedUnplug small appliances; leave one light on a timer.
Confirm passports, wallet, phone, and chargers are on your personThe pat-down check: passport, phone, wallet, keys. Everything else is replaceable at the destination.
Leave for the airport three hours before an international departureInternational check-in and bag-drop cutoffs are earlier than domestic — often 60 minutes — and are strictly enforced.

Get local currency from a bank ATM and decline dynamic currency conversionWhen a terminal offers to charge you in your home currency, always choose the local currency — the "convenience" markup runs 5–10%.
Activate the eSIM or local SIM and text your itinerary contactConfirm you can receive the bank's verification texts before you need them.
Note the address and phone number of your embassy or consulateAlso save your accommodation's address in the local language for taxi drivers.
Set medication times against the new time zoneFor time-critical medications, work out the new schedule once, on paper, instead of improvising dose by dose.