Gov.uk has some useful information on Neighbourhood Planning available at https://www.gov.uk/guidance/neighbourhood-planning–2.
Wiltshire County Council also has some excellent pages available at http://www.wiltshire.gov.uk/planning-neighbourhood.
Locality is a national organisation which, amongst other things, provides grants in support of Neighbourhood Plans. Their website has some excellent pages on the process of developing Neighbourhood Plans, including this Roadmap Guide.