How do I stop my child from hitting other kids?

Many toddlers hit when they want something, are impulsive and do not know how else they can get something they want, i.e. by asking for it or by 'using their words'. If you see a pattern when he will likely hit, pre-emptively provide him with the words/ phrases that he has to use to get what he wants or to say what he does not want. In other words, provide him with a more acceptable way to achieve his aim (using words) rather than by using physical action. Praise him if he 'uses his words'.