Do not do it!
This used to be a page about how to double dig your garden but things have moved on and now over cultivation of soil is linked with soil erosion and the extensive use of artificial fertilisers which contribute to climate change. It has been shown to severely damage soil.
After the no-dig square metre bed trials in 2010 we decided never to dig again. Not only does digging damage soil it is a complete waste of energy!
The no-dig approach certainly works but caring for soil is very important. You will need to adopt new strategies to avoid soil compaction including; not walking on the soil and keeping off heavy rain in winter and above all keeping the surface covered by mulch at all times.
Updated 30 May 2019