Fish of FuryA good tactic is the Fish of Fury. This reffers directly to the Devilfish APC which can be attached to a squad for eighty points. Loading up a squad, shipping them to
just within 12" of the enemy, putting the APC's broadside towards the enemy (effectively blocking assaults until the enemy goes
around the APC), and rapid firing with the Tau's Pulse Rifle.
This is a great way to protect the Tau from CC while still allowing for a massive base of fire. When the enemy gets within assault range (or rather, just outside of it) load up and relocate. Because the APC is a skimmer, it does not block LOS, but enemy units can't come within 1" without assaulting it, so it acts as a very nice barrier. Watch for Anti-Tank weaponry, though, as it can either destroy the APC leaving the Firewarriors stranded, or worse, cause it to explode and injure or pin the firewarriors.
For each one you wish to deploy, place it two inches from the last (remember, enemies can't come within 1", so the 2" gap is still covered).
This is a very basic description of this strat. There are undoubtedly hundreds of modifications to it, but I have yet to put it into use (I play Tau, read Tau tactics ['till the early morning], but have yet to enter a game).
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This is probably exactly what you need. It has a better description of the FoF and other strategies.