From an interview with Maisie Williams

Game of Thrones has had some big name actors on board since it began in 2011. While Sean Bean didn't last particularly long as Arya's father Ned Stark, Charles Dance has favoured better as Tywin Lannister.

"When I met Charles Dance he came up to me and said, 'Hello my name is Charlie,' and I just sat there and froze," said Williams
. "I found him intimidating at the beginning, just by the way he carries himself and commands this sort of respect. When he's on set everyone is just silent for him.
The way that he incorporates props into the scene or how he moves around the space; I learnt so much. And how natural he was in saying this dialogue that is not natural for someone of my age, you know it's not a natural way of saying things - it was really helpful just listening to him.http://www.ibtimes.co.uk/game-thrones-maisie-williams-arya-stark-like-justin-bieber-1442887