For many sports fans, nothing beats the excitement and unpredictability of the NCAA tournament. Now that the bracket has been unveiled, millions of you will be filling it out for bragging rights, whether it's just within your family, a group of friends or loads of strangers worldwide in ESPN.com's Tournament Challenge.

There's no right way to fill out a bracket, so we thought we'd do our part to give you enough information to make your head spin as you work your way through it. For those of you who like to pick each game individually throughout the tournament, College Hoops Pick 'em offers a different way to show off your prognostication skills, where you're rewarded for picking upsets.

Some of the trends below are more complex than others, but why not start off with one historical absolute that's not worth questioning:

108-0!
That's the record of No. 1 seeds against 16-seeds, and only 11 times have they won by single digits (with the last time being in 1997). Needless to say, 16s don't seem to be getting any closer to that elusive first victory.

In the past five years, not only have all but one of the 20 meetings been decided by 16 points or more, but the average margin of victory for the No. 1s has been 29.6 points.

And while you're at it …
You might as well put the No. 2s through to the third round (Round of 32) as well. In 27 years, only four times has a 15-seed knocked off a 2-seed, although it hasn't always been a cakewalk.

While it's been 11 years since the last time a No. 15 won (Hampton over Iowa State), in 18 of the previous 27 years of the 64/65/68-team field, at least one No. 2 seed has been played to within single digits or lost. However, in the past three tourneys, No. 15s haven't provided much of a challenge, with the only exception being Robert Morris' tough overtime loss to Villanova in 2010. ... MORE

Need more help in filling out your bracket, here are some other tools at your disposal:
Mass: Upsets to target in your bracket
Keating/Brenner: 10 early upsets
Lunardi: Tournament tips
Bracket predictor

• President Obama's Entry

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  Our 44th president took time out of his busy schedule to fill out a bracket in the game with our own Andy Katz. Watch the video of him making his picks and check out his entry to follow along with his picks to see where he stacks up against the rest of SportsNation. - Click here

• Challenge LeBron

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  Think you can take on one of the world's best basketball players? Challenge LeBron James in Tournament Challenge and see how you stack up! Also, follow @lebronjamescom on Twitter for giveaways during each round of the tournament. - Click here

• Challenge Mike & Mike

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  ESPN Radio's Mike Golic and Mike Greenberg are ready to fill out their "brackets of integrity" and are waiting for you to prove you can fill out a better bracket. Join the Mike & Mike group today. - Click here

• Go Around The Horn

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  Challenge your favorite "Around the Horn" personalities in the Tournament Challenge! Sign up today and see whether your bracket will end up at the top of the leaderboard. - Click here

• Challenge The Herd

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  ESPN Radio host Colin Cowherd wants to see whether you know your college basketball. Compete against the whole Herd crew. - Click here

• Be part of SportsNation

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  By being a fan of ESPN's Tournament Challenge, you're part of SportsNation. Colin Cowherd and Michelle Beadle are inviting you to be part of SportsNation and predict a better bracket than everyone on the SN staff. - Click here

• Pardon The Interruption

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  PTI has covered the college basketball season and has made their bold predictions. Join the PTI group and see whether you can predict the tournament's "Big Finish." - Click here

• Challenge Boston PG Rajon Rondo!

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  Rajon Rondo has set his bracket! Will you be able to top the guard in Tournament Challenge? - Click here

• Dan LeBatard Is Highly Questionable

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  Dan LeBatard and his father, Papi, appear daily on ESPN2 and address the biggest questions in the sports world. After all the discussions and debates, do you think they can pick the perfect bracket? Join the group and find out - Click here

• Challenge The SVP Show

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  Scott Van Pelt and Ryen Russillo are ready to take on all challengers. Join the SVP Show group and compete against everyone who makes the SVP Show one of your favorites to listen to on ESPN Radio. - Click here

• BALL BOYS on ABC

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  Every great moment in sports leaves something behind. What will the guys at Robbie's First Base take away from the tournament? Join their group and find out. The show debuts on ABC at 3 p.m. ET on March 24. - Click here

• Challenge the ESPN.com Fantasy Editorial Team

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  Picking a perfect bracket isn't easy. Neither is beating the fantasy editorial team in Tournament Challenge. Challenge your favorite fantasy writers today. - Click here

• Predict the Unpredictable with ESPN America

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  Live in Europe? Join ESPN America's Tournament Challenge Group. Challenge our talent and your fellow European hard court fans to win big. - Click here