| Staffan Johansson |
OK, here's how I think it works if you want to sneak up on someone or a group.
As soon as you or your party comes into contact with the enemy, you enter Encounter mode. If you were using the Sneak tactic, you get to roll initiative using Stealth.
Any creature who beats you on initiative and can reasonably detect you will perceive you. If you're sneaking a bit ahead of the rest of the group, them rolling poorly on their initiative checks won't make them detected, since they're out of the way (but will need to spend actions/rounds to get anywhere.
If you're still unseen when your turn comes up, you need to use Sneak actions to remain that way and move around until you get into a position where you can perform whatever dastardly deeds you came here to do.
Is that about right?