Louisville 2013
Last year only 28.5 percent of the brackets submitted to Yahoo!Sports accurately predicted Louisville as the champion. Reuters

The NCAA Tournament, better known as March Madness, once again takes over the country with office pools, paper brackets and upsets galore on Sunday.

The annual men’s basketball tournament to decide the nation’s best college team begins with 68 schools, and in a matter of three weeks a champion is crowned. This year the Final Four and championship game takes place at AT&T Stadium in Dallas.

The No. 1 seeds in this year's tournament are Florida, Arizona, Wichita State and Virginia. The Gators were the favorite to snag one of the No. 1 seeds, as were the undefeated Shockers. Arizona fell to UCLA in the Pac-12 conference title game, but its overall resume resulted in a top seed. It's the first No. 1 seed in Wichita State's history, and the fourth one for Virginia.

Florida is the highest ranked of the top four seeds, but that won't make a run to the title easier. The Gators may have to contend with Kansas or Syracuse at some point in the South region. All three teams were ranked No. 1 in the country at one point during the regular season.

Defending champion Louisville made a late season surge and could have been in play for a No. 1 seed, but was instead bumped to a No. 4 seed in the Midwest region.

Office pools, legal or not, have become part of the March Madness tradition. Bragging rights and a hefty winning sum have been the prizes for years, and according to a report from NBC News last year as much as $2.5 billion is wagered.

This year some of the heavy favorites to win it all include Florida, Wichita State, Arizona and Kansas, according to Vegas Insider.

But the key to winning the entire pool comes from finding and or avoiding the upsets stashed deep inside the four regions. The challenge of picking all Final Four teams correct is extremely daunting, with Esquire reporting only 47 out of 8.15 million brackets filled out at ESPN.com made the right prediction.

Within the four regions teams are seeded from one to 16. Esquire broke down the percentages, and eighth seeded teams beat out nine seeds only 51 percent of the time in the opening round. In the second round no. 10 seeds also beat no. 2 seeds 40 percent of the time.

Last year only 28.5 percent of the brackets submitted to Yahoo!Sports accurately predicted Louisville as the champion.

With the tournament expanding to 68 teams with one additional play-in round, most pools and sites will have you confirm and submit picks by Tuesday. That leaves would be winners and losers one-and-a-half days to make their picks.

The first round begins at UD Arena in Dayton, Ohio with the last four teams in trying to make it to the 64-team field. The second round then begins on Thursday, March 20.

Printable brackets can be downloaded from CBS Sports here, at Yahoo Sports! as part of the “Billion $ Bracket Challenge”, ESPN here, as well as Fox Sports here.

All four sites have access to a paper bracket as well as their online pools. The brackets will go live on every major site as soon as the teams are named on Selection Sunday between 6 p.m. and 7 p.m. EST on CBS.