When will my baby start responding to his name?

Usually by 9 months. Most babies should respond regularly to their own name around 9 months. They are probably not doing much talking at this age, but you should hear a lot of babbling. Most babies are saying "dada" or "mama" at this age, but it may not be specific for you.
Around 5 months. Most infants will start to respond to their name at 5 months or older. Use your baby's name frequently when addressing them from the beginning of life. If you are using a nickname instead of their given name this is what they will respond to over time.