Clear the site of weeds and rubbish. There could be hidden dangers, such as, potentially harmful plants. Always wear gloves, especially on waste ground. Try to involve your local community as much as possible in your project so that they feel it belongs to everyone.
When planting up the garden you could include labels with plant names to help people find out more about the plants in the area. Add interest by including the common name and the Latin name of the plant, what it may be called elsewhere in the world, where it originates and its purpose in the garden.