In the last Limited format (CBS), I mulliganned a lot less often than usually only because of the cards-in-hand cards like Okiba Nightwatch or Spiraling Embers. The current Limited format seems as if it's stabilized to a "normal" amount of mulligans that should be taken. You might even mulligan more often than usual because of the common dual lands; they are the easiest way to catch up with your opponent in cards. I'm sure you've all read an article that thoroughly discusses the theory of mulliganning, so I'll list the criteria once more and discuss them briefly:

• The amount of the mana-sources in your hand and deck
• The quality of mana-sources in your hand and deck
• The amount of spells in your hand and deck
• The quality of spells in your hand and deck

"Lands and spells" is not enough. In most Limited games you won't even reach the other half of your deck so your opening hand has to be good as it's at least one-third of your complete draw.

Mana-sources: What can I say, you need enough lands to cast your spells with. You don't want too many lands either, and you'll have to judge by your deck's mana curve and the amount of lands left in your deck whether or not a hand has enough lands. This is not enough though, it's another problem if your mana-sources don't fit the spells you have in your hand or the cards in your deck (color-requirements).

Spells: Too few spells is the same problem as too many lands, and your spells have to be good with each other as well. An example is four combat tricks and three lands; you've got lands and spells but no creature to play all those spells on. If the quality of the spells in your deck is good, you should also be inclined to mulligan more aggressively, since your spells will probably be better than theirs so you need less spells to win the game with.

The first deck:
10 Forest
7 Plains
1 Elves of Deep Shadow
1 Votary of the Conclave
1 Farseek
3 Fists of Ironwood
2 Seeds of Strength
1 Selesnya Signet
2 Benevolent Ancestor
1 Carven Caryatid
1 Congregation at Dawn
1 Devouring Light
1 Greater Mossdog
1 Sandsower
2 Scatter the Seeds
1 Conclave Equenaut
1 Root-Kin Ally
1 Siege Wurm
2 Guardian of Vitu-Ghazi

This is a deck I had in a Magic Online draft about a week ago, it's a straight-up Selesnya deck and the only thing you're missing really is Selesnya Evangel and maybe some more removal. It has three Fists of Ironwood and double Scatter the Seeds to replace Evangel though, and enough fatties to kill your opponent with; I'd say this is quite a good deck.

Hand 1 (on the draw):
Guardian of Vitu-Ghazi, Benevolent Ancestor, Seeds of Strength, Votary of the Conclave, 3 Forests

We've got lands and spells, but we can't cast any of them and even if we draw one of eight White sources (7 Plains and 1 Selesnya Signet) the hand isn't great as it is. If you draw Fists of Ironwood or Scatter the Seeds, the hand is quite good but for this to happen we need both the Plains and one of five token-generators. This deck is too good to take this gamble; I'd mulligan.

Hand 2 (on the play):
Belevolent Ancestor, Scatter the Seeds, 3 Forest, 2 Plains

There are too many lands in this hand, but the Ancestor helps you to stay alive and Scatter on turn 4 makes sure you can play any fatty you draw. You're on the play, so if you draw one of five fatties (including Conclave Equenaut) or Congregation at Dawn in four draw steps you'll have it in play very early. I'd keep this one.

The second deck:
7 Forest
1 Plains
6 Swamp
2 Golgari Rot Farm
1 Selesnya Sanctuary
1 Gather Courage
1 Clinging Darkness
2 Fists of Ironwood
2 Golgari Signet
1 Civic Wayfinder
1 Golgari Brownscale
1 Putrefy
1 Sadistic Augermage
1 Dimir House Guard
2 Faith's Fetters
1 Greater Mossdog
1 Keening Banshee
2 Mortipede
1 Strands of Undeath
2 Bramble Elemental
2 Scatter the Seeds
1 Siege Wurm

As you can see, this deck is a lot worse than the first one; it's got many bad cards. Even the Scatter the Seeds aren't so good because the only creature they accelerate into is Siege Wurm. This deck is rather mediocre.

Hand 3 (on the draw):
Swamp, Plains, Dimir House Guard, Sadistic Augermage, Greater Mossdog, Scatter the Seeds, Strands of Undeath

This hand is missing mana; both quantity and quality. If you draw a Forest and another land, the hand will develop into an okay draw, and if you draw a Swamp you can transmute for the best spell in your deck: Keening Banshee. The quality of your spells isn't great, but hey, that's the deck. If you look at what lands you can draw, three of them are dual lands which would cause you to discard a card, and if you mulligan into one of these lands or Civic Wayfinder, it'll undo the mulligan for you. I'd mulligan this one.

Hand 4 (on the play):
Golgari Rot Farm, Selesnya Sanctuary, 2 Swamps, Forest, Clinging Darkness, Mortipede

This hand has lots of mana and all three colors you need, but only two business spells and the Mortipede is quite bad if it's not backed up by some other creature you played earlier as it'll be likely to trade for just a 2/2. Clinging Darkness helps with this though; you'd just play it on your second or third turn on a random 2/2 to help you stay alive long enough to find business spells. The mana-base of the deck isn't so good and even though you have a lot of cards to undo mulligans, I'd keep.

I'm not sure if these examples were very good as I didn't have time to ask for insights of any other players, so please let me know in the forums about them or post a tough mulligan decision you had to make, and don't forget to add information about the deck; the decision relies on that a great deal. Oh, and I'm open for suggestions for tomorrow's subject, if anything you suggest interests me I'll try to write about it.

-Julien