Sam Ernst, one of the creators of Haven, answered some questions and gave some hints for the second season on Twitter:
Q) @nancye_200 I'm intrigued by Julia, is she going to be around in S2?
A) this one I better not answer :)
A) yes, some of the guest stars will reappear. Starting in Ep 202 - but you need to be on your toes to see them.
Q) I do actually have intelligent TV questions but they all get eclipsed by, "when are Audrey and Nathan going to make out already?"
A) She needs to make out with someone, doesn't she? (And she will.)
A) We LOVE Vince and Dave. make us laugh every single time. yeah, there's more of them. And more ABOUT them, too.
Q) @detectivejane "How drastically does Audrey knowing that Nathan can feel her change their relationship?"
A) Hugely! Episode 202.
Q) A reference to Flagg this season would be fab.
A) very first scene of ep 201 is my favorite King ref! RT
A) Season two will have 13 episodes, ummm, sort of. (Can't say more).
Don't forget to follow Sam Ernst on Twitter: @havensam