From the Proxy posted on the UPS Investor relations website:

What do I need to show to attend the annual meeting in person?

You will need proof of your share ownership (such as a recent brokerage statement or letter from your broker showing that you owned United Parcel Service, Inc.’s stock as of March 10, 2008) and a form of photo identification. If you do not have proof of ownership and valid photo identification, you will not be admitted to the annual meeting. All bags, briefcases and packages will be held at registration and will not be allowed in the
meeting.