I don't have to think about the answer because I know ;D. I would stay true to myself and I'd be nice.
I'd be polite to my fans and to the press (even when they make it difficult, because I made a choice, I decided to make my life public, and - like in every situation - there are some pros and cons.
I'd sing all the autographs and I'd be always ready for a selfie. I would be very similar to David Tennant on the matter. I would keep my personal life personal, and stay away from useless gossip, but I would be on socials at the same time (because that's who I am, I like my socials) but I'd prefer quality over quantity.
I would go to ComiCon and go nuts... I would always be there for my fans because and - since I love TV shows - I would be totally invested into my show (I'm assuming I'd be an actress here).