In the next few days I'm heading over to Manila, Philippines for work reasons.
I have never been to APAC in my life and I'm looking for some non-Google answers that would help.
What should I be concerned about when visiting Manila for business?
This answer is going to focus on going to Manila for business, which is pretty different to going to Cebu on a beach holiday!
The single most useful tip I can give is to choose your hotel's location to minimise distance to the office. Traffic is Manila is appalling and it can take hours to travel short distances, particularly when it rains - I spent over three hours going from BGC to the airport last year, which is a distance of barely 10 km.
Second, dress up, even if you work in a casual industry like IT and even though it's hot and sweaty outside. Collared shirts and decent trousers (khakis are fine) are expected, and many BPO offices ban shorts. A full suit and tie would be overkill though, unless you're in sales or banking.
Third, be careful with credit cards, cloning is a major concern and acceptance is low anyway. Withdrawing cash from an ATM is the best way to go. Try to keep smaller bills on hand, 1000 pesos is a lot by local standards.
Fourth, most of Manila is poor, opportunistic crime is common and foreigners are attractive targets. You'll almost certainly stay and work in the rich parts of town, like Makati and Taguig, which are full of heavily armed police and very visible security for this reason. Nevertheless, don't flash your wealth when out and about in town: leave the laptop at the hotel, keep your camera in your bag, think twice before pulling out your iPhone, consider using a money clip instead of a bulging wallet. Go with friends, preferably local ones, if sampling the nightlife (and you should, Filipinos know how to party!).
Finally, some good things. Disease is not a major concern, if you're staying in decent offices and working in air-conditioned offices there's no need for extra vaccinations, malaria prophylaxis, etc. English is also spoken by virtually everybody, so there's no need to brush up on your Tagalog (although a few words will be appreciated!).
(I put reference to US web sites, but other countries have similar information)
Check with your doctor for applicable vaccines and related drugs. If I remember correctly, some vaccines and drugs need to be taking some times before traveling (days and weeks), so plan accordingly)
Check your travel papers; a valid passport (at least valid for 6 months) , visa if applicable, and any other travel document needed.
I don't know the state of Credit card/debit card in the Philippines, but I assume that in Manilla itself , you should be ok (warn your card provider that you will be traveling there to reduce the risks of your card be blocked).
Check the weather (rain or typhoon season might not be the best time to go there.)
Check before traveling in some areas of the Philippines:
Other than that, keep an open mind and open eyes and enjoy.