What is this and why is it helpful?
In worship, it is easy to forget that we are a community gathering in the presence of God to celebrate the transforming love of God with each other. 'Sharing the peace' with one another is a demonstrative act of community. Everyone is included. This is how we say to each other: 'We are here together in the presence of God, and I acknowledge before God that you count too!'
Where you place 'the peace' in the service/gathering is also important, as there are good reasons for it being in different places. For example: having it at the beginning as it emphasises the community coming together; or if you have it before communion, it is an opportunity to get straight with God or with others; or some share 'the peace' towards the end of the service (usually after communion) to emphasise the importance of being together as a means of grace that flows into everyday life.
The way in which the peace is shared needs to be sensitively handled as it is easy to step over the hidden boundaries of other people's 'personal space'. Greeting one another with great big bear hugs can be too much for some people, but equally, just the limp shaking of a hand can be a less than dynamic expression of togetherness. One thing that is important is hospitality and welcome, so one must always guard against only greeting your closest friends, but also be aware of greeting the stranger in an appropriate manner.