Lust for War

(15/06/2010)
Lust for War's triggered ability triggers when the enchanted creature becomes tapped for any reason, not just when it attacks.

(15/06/2010)
If, during its controller's declare attackers step, the enchanted creature is tapped, is affected by a spell or ability that says it can't attack, or is affected by "summoning sickness," then that creature doesn't attack. If there's a cost associated with having that creature attack, its controller isn't forced to pay that cost, so the creature doesn't have to attack in that case either.