^^ add ko lang sis. Allot extra time to be in the airport for your departure flight. Para me allowance ka for long checkin/immig lines. If available, use the online checkin facility of your airline, this will save you time. Also, have pesos ready for your terminal fee, etc. Also have some USD handy, panggastos mo during layovers and upon arrival, while waitng for your sundo (pantawag, etc). San ang layover mo? You can approach the flight attendants or the airport staff to help you locate your transfer/boarding gate during layovers. Double-check your boarding gate for your connecting flight (if necessary), because sometimes they change gates at the last minute. Listen to airport announcements.
For check-in luggage, make sure na me lock. And as much as possible, do not put high-value items like jewelry and such. I-handcarry mo na lang mga yun. If me dala ka babasagin, wrap it ng maayos para in case mabasag e hindi kakalat to your clothes and other things.
For your handcarry, you can bring one extra set of clothes (don't forget undies). And mind the restrictions on liquids (not more than 100ml per item, no lighters, etc), also no nailcutters and other sharp objects. If maglalagay ka bag sa overhead bin, make sure na me lock. You'll never know, baka me magkainteres while tulog ka or when you're not looking. Keep important documents like passport, wallet, itinerary, etc in your handbag or sling bag, which you can hold on to or put under the seat in front of you. And always bring this hand/sling bag with you kahit magsi-cr ka lang. Yung nasa overhead bin na me lock, di mo na kelangan bitbitin.
Do not easily trust strangers. Scan or photocopy your passport and visa, this will come in handy just in case you lose your passport (pero wag naman sana...).
If takot ka sa heights, do not get a window seat, baka lalo ka nerbyosin. Aisle seat ka na lang. Wear comfortable clothes (and comfy footwear) especially since long flight ka. And, be careful not to mention "bomb" sa airports and sa airplane, kahit joke lang. This can get you offloaded and fined.
Sa immigration, both here and sa US, kung ano ang itanong yun lang sagutin mo. Kumbaga isang tanong, isang sagot. Less talk, less mistakes. And be consistent sa sagot mo. If tourist visa ka, pag tinanong itinerary mo, then it should match that of a tourist/visitor. If fiance visa, then be prepared to answer clarificatory questions about your boyfriend and your relationship.