From an interview of M.Williams

Q: How was it doing scenes with Charles Dance?

MW: I just got on with him really, really well. He was a little bit intimidating but I think that helped a lot with the script and stuff because Tywin (Lannister) is supposed to be intimidating. Charles is just a really, really lovely guy and I learned a lot from him as well. When we did the reverse shots in our scenes he sat in for my lines. He could have gone home and someone else would have read his lines but he said, "No, it’s fine, I’ll sit there," which was really nice. I tried to make a good impression because being a child actor, you’re always proving yourself. But I really liked him, he was funny.

Q: What has been your favorite scene over the last two seasons?

MW: It was when I was doing that scene with Charles Dance and I say, "Anyone can be killed." It felt like when you’re acting on a stage, and you either have the audience or you don’t. I did it on my close-up -- and I just felt like I sort of meant it, you know? It was all quiet and it took a couple of beats until someone said "Cut!" and then it was like, a charged atmosphere. I felt good after that. It’s that feeling: I don’t get it so much from acting but every now and then it comes up and I can’t describe it. I get it a lot more dancing -- it’s just a little buzz that you get. That’s why you go to work I guess

http://www.bworldonline.com/content.php?section=Weekender&title=Maisie

Which was your favourite Arya’s scene so far?
Maisie Williams says:

My favorite scene to watch with Arya in was Ned's beheading. My favorite scene to actually act in were the scenes with Charles Dance as Tywin. Reading them on the paper I was nervous to be working with Charles because I've seen him act and never met him but coming into shooting he was such a nice good and enjoyed the scenes very much!
http://connect.hbo.com/events/game-thrones/q-maisie-williams/