In the books, I found him [Sherlock] to be a much more understanding guy. I feel that he really likes people a little bit more than I had seen recently – not that he can necessarily communicate that very well. He likes the underdog, and he likes people who are downtrodden, who are having a hard time. He generally wants to help. I found him to be a much more helpful person, so I tried to put a bit of that in, even though he doesn’t quite pull it off.
Jonny Lee Miller [Hollywood Reporter, 18 June 2013]
In the same interview, Miller also describes how he physicalizes the role of Sherlock Holmes. In particular, he notes, “I wanted him to be quite wild and erratic physically. I felt that that matched his brain; it’s almost what you see in people whose brains are moving very fast, and who are struggling [at the same time]. They often have those characteristics, physically. You don’t want to overdo it, but if you do it regularly, then it seeps subconsciously into the character, and people recognize things”.
An interesting insight of Sherlock from the actor himself.