How do you answer a phone call?

In general, the standard is:

Hello?

In jest, when you've had a slew of calls:

Grand Central, how may I help you.

In more specific business circumstances:

Boss's telephone: Good afternoon, Ms. Boss's office.

Retail store: Thank you for calling BigBoxStore, how can I help you?

Main number at a large workplace: Good afternoon, XXX corporate offices. How may I direct your call?