Sort the bags first
Everything else on a checkout day depends on this. Most accommodation will hold luggage for departing guests, and the way to make it reliable is to ask the evening before, confirm the hours the desk is staffed, and note whether you need a receipt or tag.
If you are collecting the bag later, choose your day's activities around that location rather than the other way round. A morning museum on one side of the city followed by a bag pickup on the other and then an airport run is a plan that looks fine on a map and falls apart in the afternoon.
Decide the departure time before you plan the day
Work backwards, and be honest about each step.
Start from your airline's check-in cutoff, not the departure time, since international check-in closes well before boarding. Add the security and immigration queues. Add the road journey from wherever you are collecting your bag. Then add a traffic allowance that reflects the actual hour: a late-afternoon or early-evening run through Metro Manila is the slowest version of that journey, and there is no route that reliably avoids it.
Whatever number that gives you, the time you leave is a fixed point, and the day gets built around it.
Confirm the terminal
NAIA's terminals are separate buildings connected by road rather than a single concourse, so arriving at the wrong one is not a five-minute correction. Check the terminal on your booking, and if it only says NAIA, ask the airline.
If you do end up needing to move between terminals, the airport runs a free inter-terminal shuttle for passengers with connecting flights, boarded by presenting your onward ticket, but relying on it to fix a mistake on a departure day costs you the buffer you built.
What to do with the hours
The best checkout days in Manila are geographically small. Pick one district, ideally the one where your bag is, and spend the day there.
Indoor options carry the afternoon well, particularly in the rainy months or the hot dry ones, and large malls handle several needs at once: air conditioning, food, a place to sit with wifi, and often the currency counters and pharmacies you might want before a flight. A long lunch is an underrated way to spend a departure afternoon.
What does not work is a plan with a fixed start time somewhere across the metro area, or an outdoor activity that leaves you overheated an hour before you need to be presentable on a long flight.
Money before you go
Two loose ends worth closing.
Spend down or convert your remaining pesos. Central bank rules allow bringing in or taking out Philippine currency up to 50,000 pesos freely, so for most visitors this is about usefulness rather than legality: leftover pesos are simply dead weight once you land elsewhere.
Keep a small amount aside for the airport itself, in case you want food, water or a last purchase before security, and remember that anything you spend after check-in is a poor place to be discovering that a card is declined.
At the airport
Give yourself time to be unhurried. The airport publishes its amenities by terminal, including clinics, charging stations, currency counters and free wifi in passenger movement areas, and a departure with an hour of slack is a completely different experience from one without.
If you have checked bags, get them checked in and get through the queues before you sit down anywhere. The comfortable part of a departure belongs after the formalities, not before.
A simple checkout-day shape
Agree bag storage the night before. Check out on time. Keep the day within one district and near your bag. Eat properly in the early afternoon. Collect the bag with a wide margin. Leave for the airport earlier than feels necessary. Spend the last pesos before security. Then sit down.