How does Suprise rounds work?

[1bent1]

I am having a problem determining how a surpise round works. this is the Senario 1:
3 NPCs (1, 2, 3) are waiting to attack 4 PCs(A,B,C,D). The NPCs make stealth checks and the pcs make oppossed percepton checks. NPC 1 is onle precieved by Pc A and not by PC B, C or D. NPC 2 & 3 are precieved by all PCs.
Who gets to act durring the Suprise Round?

Senario2:
3 NPCs (1, 2, 3) are waiting to attack 4 PCs(A,B,C,D). The NPCs make stealth checks and the PCs make oppossed percepton checks. NPC 1 is onle precieved by Pc A and not by PC B, C or D. NPC 2 & 3 are precieved by A,B,C but not D.
Who gets to act durring the Suprise Round?

Clarifcation on this would help. My party and I can't agree on how this is supposed to work and we all want to be on the same page.

THANKS IN ADVANCED.

[Beckett]

Those that notice any of NPC's 1, 2, or 3 get to act in the surprize round (wwhich is only a single Move OR Standard action). So, if they do notice an enemy, they roll initiative, and then do their surprize round action in that order. Anyone that didn't notice an NPC, would roll initiative, but not get to act until the round after the surprize round.

Note, that if they do not notice a particular NPC, (but did notice others), they can not target them or attack them.

So, in both scenarios, A could attack anyone, while B & C can attack 1 & 2 only. In Scenario 1 D could attack 2 & 3 as well, but not in scenario 2, and actually is the only one that can not act in the Surprize round.

[SteelDraco]

I would typically only roll one Perception check per PC to have them notice an impending.ambush. Anyone who saw an enemy waiting for them would get to act in the surprise round, rolling initiative as normal. Remember that surprise/rounds are only a standard action, though, so you're limited on what you can do.

[JohnF]

SteelDraco wrote:

I would typically only roll one Perception check per PC to have them notice an impending.ambush. Anyone who saw an enemy waiting for them would get to act in the surprise round, rolling initiative as normal.

That's how everybody I know does it, too.

SteelDraco wrote:

Remember that surprise/rounds are only a standard action, though, so you're limited on what you can do.

As with almost everything in Pathfinder, there are feats or items that modify this. For example:

• If two characters each have the teamwork feat Lookout, they can sometimes get to take both a standard and a move action (or a full-round action) in the surprise round.

• Sandals of Quick Reaction also allow the wearer to take both a move and a standard action in the surprise round (although a full-round action is not explicitly mentioned)
  

[1bent1]

The Pcs each made one perception check, so they did not roll for each stealth check but checked the roll vs the the stealth rolls.

So both side could act in the suprised but not against those they did not precieve. and if a person does not precieve any of the enemy they can not act?