Hmm...I'm not really sure. I just focus 
I don't have any routine habits I must do like tapping or music (although I usually listen to music when playing online; I've also done equally well with complete silence). In all honesty, I think the best way to "focus" in chess (or anything really) is simple to get good at zoning out the things you don't want to pay attention to and keep attention on things like the game. 
For me I like to keep a rhythm by tapping my foot or my hands.
Another way to make me focus is to make my chess friends watch the game, then if I mess up they laugh and tease me so I have to play well lol