Attention, Black Friday shoppers: The world's largest retailer is upping the ante.

Wal-Mart has announced a three-stage Black Friday event, beginning at 8 p.m. on Thanksgiving. That's two hours earlier than the deals began last year. And Wal-Mart is guaranteeing shoppers who show up at the right time will be able to purchase some of the most popular gifts.

Here's how it will work:

8 p.m.: In-store specials begin, focusing on gifts for the whole family. Featured deals include video games, toys, housewares and clothing.

10 p.m.:  The focus shifts to electronics, with deals on TVs, tablets, laptops and cameras. In addition, this is the time for Wal-Mart's "one-hour guarantee." Anyone inside the store and in line between 10 p.m. and 11 p.m. local time will be guaranteed the following deals:

• 16 GB Apple iPad 2 with Wi-Fi, plus a $75 Wal-Mart gift card, for $399.
• Emerson 32" 720p LCD TV for $148.
• LG Blu-ray Player for $38.

“We know it’s frustrating for customers to shop on Black Friday and not get the items they want,” said Duncan Mac Naughton, Wal-Mart's chief merchandising and marketing officer. “This year, for the first time ever, customers that shop during Walmart’s one-hour event will be guaranteed to have three of the most popular items under their tree at a great low price.”

Wal-Mart says if any of the items sell out before the hour is over, it will give customers a Guarantee Card. The item then must be paid for by midnight, registered online and can be picked up later at the store where it was purchased.

5 a.m.: For those who prefer the traditional Black Friday experience, Wal-Mart will roll out a third wave of deals on a variety of items including jewelry, tires, hardware, furniture and Christmas trees. (Wal-Mart says store opening hours may vary by location, so check with your local store before heading out.)

There will also be Black Friday deals for those who prefer to shop from home. Wal-Mart will have a two-day, online-only event, starting Thanksgiving morning and running through Friday. It includes free shipping under certain conditions. And speaking of online shopping, the retailer has plans for an entire week of savings starting on Cyber Monday.