http://www.wizards.com/Magic/Magazine/Article.aspx?x=mtg/daily/arcana/1067

Unite together behind the banner of Selesnya, and take command of an army that adds to its ranks with every step. This deck centers around the Selesnya guild's populate mechanic, which allows you to make a copy of any creature token you control. That means your first order of business is getting a token onto the battlefield as quickly as possible.

Seller of Songbirds, Centaur's Herald, and Call of the Conclave are great token-making cards to get things started. Not only do you get creatures on the battlefield, but those tokens make populate spells like Trostani's Judgment and Druid's Deliverance substantially more powerful as they spawn a creature to go along with their regular effect. Before you know it, your side of the battlefield will be filled with too many creatures for your opponent to handle.

Remember that there's a big difference between having zero tokens on the battlefield and having one, even if it's nothing but a 1/1 Bird. That single Bird can turn into a flying armada with a couple attacks from Wayfaring Temple or get a sizable boost from Phantom General. But the token made by Grove of the Guardian is at the top of the pyramid. If one 8/8 with vigilance is difficult to deal with, imagine what it's like to contend with a battlefield full of them!

If you're looking to take this deck in a different direction, one of the best ways to go is up. Entreat the Angels from the Avacyn Restored set can summon an insane number of 4/4 flying Angels, and the 5/5 Armada Wurm brings along a 5/5 Wurm friend when it enters the battlefield. And like a true guild leader, Trostani, Selesnya's Voice can tap to populate every turn.