From the Codex:
Daze
Creature is disoriented and/or blinded. Whenever this creature makes an attack, roll the effect die at the end of the Declare Attack Step. If the result is 7 or higher, the attack is resolved normally. If the result is 6 or less, the attack “misses” its target and skips to Step 5 of the attack sequence (Additional Strikes). If it makes a Zone Attack, only check once: the entire attack either fails or succeeds normally. If a creature has more than one Daze on it, roll only one time to see if the creature misses. In addition, the Dazed creature suffers a -2 penalty to all Defense rolls for each Daze marker it has. All Daze markers are removed at the end of the creature’s Action Phase. Daze has a removal cost of 2. Conjurations cannot be Dazed.
Stun
Creature is Incapacitated. All Stun markers are removed at the end of the creature’s Action Phase. Stun has a removal cost of 4. Cannot affect conjurations.
Its real nice to do this kind of attack at the end of you non-initiative phase......you can get in two hits before he activates....