How can I develop better Empathy

Often when I go through life and see people, including friends and family, I have trouble feeling empathy for them in an emotional sense. It is difficult for that feeling to be very pronounced within me. I do try to help them, and I often have the urge to do so, but much of the time when I see people going through horrible or painful situations I feel little or nothing emotionally, with some exceptions.

For example, one time one of my good friends was crying because of a situation he was in with his girlfriend at the time. I tried to comfort him and help him through it, but even as he cried I did not feel much emotionally. Later I felt some guilt for that lack of feeling.

How can I develop empathy for others in the emotional sense? I believe I do have the capacity for it, but it is not very noticeable much of the time.