WASHINGTON - Wal-Mart Stores Inc. and other retailers are being told by the government to take greater precautions with their Black Friday shopping events to avoid a repeat of last year’s problems, when a worker was trampled by customers.

The Occupational Safety and Health Administration urged merchants to consider things like using a bullhorn to manage crowds, setting up barricades or rope lines, and clearing the entrances of shopping carts and other potentially dangerous obstacles.

The guidelines also call for using an Internet lottery for “hot’’ sales items, staffing entrances with uniformed guards, and providing public toilets.

Arkansas-based Wal-Mart, the world’s largest retailer, has said it will extend store hours to help manage crowds.