Q: What can a person do to increase the concentration and kavana (focus) in davening?
A: There is a general system, and a matter for Yom Kippur specially. In general, "Tafasta meruba lo tafasta" — You can’t do everything at one time, so concentrate on a small area. Every day you pick just one little part, let’s say one bracha, and make up your mind. "On this bracha I am going to put in all my thoughts, I don’t care how long it takes!"
Let’s say you want to say selach lanu, so you say selach lanu, and think about it, "Forgive me Hashem!", and you try to remember wrong things you did. "Selach lanu avinu!" Think avinu means our Father, Hashem loves us like a father, and we love Him like a father. Think into it... One bracha, concentrate on it, put your efforts in, even if it takes two minutes or three minutes, don’t care.
Think into one bracha, put your efforts in, even if it takes two or three minutes
After you’re finished, you know at least with one bracha you succeeded in thinking about. The next day, or next tefilla, mincha, you can study the same thing over again even more profoundly, or go on to another bracha. So by concentrating on a small amount at a time, you’re going to start succeeding in concentration and kavana.
On Yom Kippur, there’s a different attitude. Yom Kippur in addition to trying to concentrate what you’re saying, also is a function of thinking that Hashem is listening to you and he wants to wash you. You know when you were a little boy, two years old, you remember sometimes you had full pants. You were so ashamed, you climbed the steps and said "Mommy, I have full pants." So your mommy took you and took off your pants and washed you. That’s how you have to feel Hashem is cleaning you today; "Hashem my Father, cleanse me!"
You’re asking Hashem, "Kaper lanu selach lanu mechal lanu," wash me Hashem, cleanse my neshama (soul). That’s the machshava (thought) of Yom Kippur, please Hashem please. That’s an additional thought to all other thoughts.