For an outdoor garden, first decide an area.Choose a location which is sloped, as that will allow proper drainage.Then, add soil that is specially prepared for cactus so It will be easily available with the florists. You can create different patterns by adding various varieties of cactus.
Another option is one-fourth good peat (available at any store selling florists' supplies), one-half sharp sand, one-fourth good black loam, and pulverized charcoal. If your cactus grows in limestone area, you may add one-fourth part of limestone to the mixture
Read more at Buzzle: http://www.buzzle.com/articles/how-to-build-a-cactus-garden.html