Joe Swift's Design Tips for Small Gardens:
Make a master plan before you begin.
Break the garden up into three distinct areas to make it more inviting to explore. For example have stepping stones through plants in the central space, and sunny and shady sitting areas at either end.
Create a sense of space by taking paving the full width of the garden
Incorporate diagonals, angles and asymmetry in the design to disguise the rectangular shape of the garden and make a more interesting route through it.
Introduce variety by having changes in level - old railway sleepers are an easy construction material and don't usually need foundations.
A good lawn is high-maintenance: think hard about whether you want one, and if you do, ensure there is a way of walking down the garden without having to step on the lawn when wet or frosty.