You mean, like, how you answer, as in, greetings? I think the most common one is a simple "Hello." Sometimes it depends on who's calling. Hm... I don't know about other people, but I use more than one :)
Some greetings might include:
- Hello
- Hi
- Yes? / Yeah?
- Hey
- Yea, hello [Said quickly, it sounds like "yellow."]
- Who's this? [For those unknown numbers, telemarketers and money-grubbers.]
- Can I help you? [If you're unsure of the caller again]
I've also had people greet me with:
- Yo
- Oy
- 'Sup? / What's up?
- Exclaiming the caller's name in a friendly manner
^ These are very informal