[PapaBigBelly]

Once you see them trying to wall off with 2 supply depots and a Barracks, Its almost definately Banshees.

I normally get my Lair up fast, get Hydras and a few spore crawlers, Queens and Overseers.

Note that you need quite a number of Hydras to take down a few Banshees, otherwise Banshees decimate Hydras :P Mutas just seem too late and they can get banshees before the Spire is done which takes Lifetimes. Yes get mutas later as once they see Hydras, they possible might go for Tanks.

Mutas Pick off Tanks well