Do come in appropriate clothes when the occasion calls. Although the Philippines is a walkable country, not all places would welcome you in your flip-flops and shorts. Churches, government institutions and some restaurants require proper attire. Besides, if you come well dressed, Filipinos will admire you, and it's always fun to dress up!
Don't forget to laugh. Laughter is used very frequently in the Philippines: to break tension, to relieve moments of awkwardness, and to put people at ease. On the rare occasion that laughter is at someone's expense, it is usually done good-naturedly. A good sense of humor is definitely an asset in the Philippines.