There's a few misconceptions about Surprise in the nWoD.
Surprise, as defined by nWoD, is covered in WoD p.151-152 and consists of two elements:
a) architecting a scenario where the other party is unaware
b) the other party failing their PERception roll
Even if Surprise is accomplished, it simply negates their DEFense.
There are no bonus/extra Surprise Turns.
To clarify the system vs. perception, a 'surprise attack' is simply winning Initiative. It means you went before they did. It's not unreasonable to suggest Initiative Modifiers if you feel like you've 'lulled' a target into complacency; often I'll just let a player have it. I justify this with the "Initiative re-ordering" Action.
So, always roll Init. Some people have noticed in the past I havne't bothered to roll and just let them go first -- this is when I've determined they've 'gotten the drop'.
Another note is I'm also a fan of called shots/effects. Feel free to describe such, and I'll narrate whether it was successful. Most of the time it will involve over-suxxing an Attribute (STA for KO, DEX for Disarm, etc), but it will always involve a to-hit Penalty, unless an appropriate FS Maneuver or Merit is possessed.