You Can:

Invite the employee to take a seat

Explain why they are being terminated

Be direct and to the point

Clear and consistent, re-iterate if possible.

Outline separation package- if necessary

Keep meeting short as possible- max 15-20 minutes

You Can't:

Engaging in non-business related discussions

Trying to incorporate humor into the situation

Giving off the impression of sympathy

Mentioning other employees

Trying to minimize the importance of the situation

Using phrases like "I know how you feel" or "I know you'll find another job."

Making the decision a personal matter.