Help a new DM at determining random encounter suprises

[Goblin Goatbutts]

I started playing D&D a few months ago and our current DM doesn't really like DMing. I really want our group to stay together so I bought OotA and plan on running it in a few months. I am still in the reading and research stage with OotA and like I said, I have no previous DM experience.

On page 20, under Noticing Threats, there are 3 conditions on how adventurers can achieve surprise. The last condition seems unclear to me "At least one party member is capable of noticing the threat and communicating it to the rest of the group". Is this based on passive Wisdom versus the enemy Stealth check or what? How does this rule come into play?

Also how do I decide when the players are surprised? If they do not notice the threat (whether it IS against a Stealth check or whatever the rule) are they automatically surprised? Does that mean when traveling at a slow pace, all encounters are surprise encounters (whether the players or the enemy)?

 

[kalani]

Normally, you determine whether one group is aware of the other group by comparing their passive perception (wisdom) scores against the enemies stealth. If the group is not being actively stealthy - this would be a Passive Perception (Wisdom) vs. Passive Stealth (Dexterity) check.

If you are already aware of one group's presence, you don't need to make passive checks. You already know they are there and cannot be surprised. Determining surprise only occurs if there is uncertainty whether you are aware of the enemy group or not.

As stated in the PHB, you make these checks separately for each character (PC and NPC alike).. Any PC who fails to notice the enemy is surprised, and cannot act during the first round of combat. The same also applies in respect to any enemies which fail to notice the PCs.

Ambushes: The ambushing party is already aware of the other side, so do not need to check to see if they are surprised.
Both Parties surprised? An example of this being that both groups meet around a blind corner without either being aware of their presence beforehand.... Both groups check to see if they are surprised as above, resulting in the possibility of some (or all) characters on both sides of the conflict being surprised.