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!
Do expect to be invited to the homes of Filipinos. They will invite you to help yourself to everything and anything on their dining table, and they would appreciate it if you partook of the food offered. If you happen to show up during meal time, an extra chair will made available to you. In short, do eat when you're offered food. Don't offend your hosts by refusing outright.
Do be sensitive to household customs. If you happen to see shoes or slippers outside your host's abode, you may be asked to leave you footwear outside also. They will offer you house slippers, or if they don't, the house floor is most likely clean.