In most casual contexts, it's easy to say hello to Filipinos - you can do so in English, as most Filipinos are quite adept at the language. But you can score points by greeting them in the Filipino language. "Kamusta?" (how are you?) is a good way to say hello, for starters.
If you want to refer to the time of the day, you can say:
"Magandang araw" - "good day"
"Magandang umaga" - "good morning"
"Magandang hapon" - "good afternoon"
"Magandang gabi" - "good evening"
When saying goodbye, a nice (but rather formal) way to take your leave is to say "Paalam" (goodbye).