Can you use a standard bulb in a 3-way socket?

Most sockets require you to have a matching bulb. A mogul socket would require a mogul bulb and a GU-24 socket requires a GU-24 bulb. 3-Way sockets do not have the same requirement. I would say that most 3-way sockets probably don't have 3-way bulbs in them because they can operate a standard light bulb.

How can you tell if the socket is 3-way?

You can look inside the socket for the second bulb contact.

Without removing the bulb, you can tell a three way just by turning the knob as demonstrated in this video:

3-Way bulbs aren't for everyone. They are more expensive than standard bulbs and in some instances they might be too bright.