Now that EW is officially released, I figured people are going to want to know how the new keywords work. Nothing is official till its in the FAQ, but they OK'ed me putting these out here as guidelines until a new FAQ is released.
The Ambush X keyword is active even when on a facedown development. During the Ambush step of the Battlefield Phase, the defending player chooses cards in the defending zone he wishes to Ambush and pays their Ambush cost (denoted by X), then they Ambush.
If the ambushed card is a unit, it must be declared as a defender for the current attack (it is not immediately declared as a defender when it ambushes). If the ambushed card is a tactic or has a “When this unit ambushes” effect, then it follows normal triggered action rules and must be put on the chain at the next available opportunity.
Immediately after combat damage is applied, the controller of each surviving, attacking unit with the Raider keyword gains resources equal to its Raider value.
The Raider keyword triggers even when no damage has been dealt during combat, provided the unit with the keyword participated and survived.
… Declare attackers, play actions, Ambush step, play actions, declare defenders, play actions, …