A full assessment requires specialist expertise and resources. Unless you have such expertise you would be advised to consult the capability evaluation literature and the DERA and Lloyd's Register experts listed on the contacts and links page.
The steps involved in conducting an HFI PRA Process Improvement exercise, conducting an HFI PRA assessment and the use of the HSL model to support planning are given in the Assessment Model in the HSL Standard download as zip and are also elaborated in ISO 15504 Part 2 or SEI CMM.
This page gives an informal outline of what is involved in carrying out an assessment. The number of steps outlined below may give the impression of a major procedure. However, even in a large scale PCAE, many of the steps will be very brief.
Review project (as part of normal business)
Decide reason, scope and scale of assessment
Conduct preparatory activities
Build assessment team
Develop assessment materials
Conduct assessment (interviews)
Analyse results, present to the assessees and resolve differences
Produce agreed findings and promulgate findings
Put follow-through actions in place (as part of normal business).