If you have access to partnersource you can download this detail.
Essentially it is a staged methodology for successfully implementing an ERP solution. The stages you go through, the sign off points, the expected results and decisions at each stage, that sort of thing really.
Vjeko Babic has made a number of posts around Sure Step on his blog. Here is a link to the posts: http://dynamicsblog.wordpress.com/category/sure-step/