Wait for a count of 10 in your head before inhaling the second breath, and repeat this form of breathing until your body feels heavy and warm, and you can actually feel the blood coursing through your veins. This works because you are slightly lowering the oxygen content of the blood. It will take more time for a beginner, so don't give up if you do not become centered immediately. It may in fact take a few sessions before you calm the mind enough to center yourself. When some people are fully conscious of the power of their own pulse and heartbeat they make comments that their body feels to be vibrating, or oscillating.
Many people live their entire life without ever becoming conscious to the strength of their pulse.
A busy mind seems to completely mask the pulse, and minor pains. I refused to accept it. 1 year ago, I fell and broke two bones in my right foot, and also had a partial tear of the Achilles tendon, along with nerve and muscle damage. I fought back from that. Today I walk with a very slight limp.