Grey literature needs to be critically assessed to make sure it is credible. It needs to be of the same high standard as other sources of information you are citing in your research.
The AACODS checklist was created by Jessica Tyndall from Flinders University Medical Library. The checklist includes the elements you should use when evaluating grey literature:
Tyndall, J. (2010) AACODS Checklist. Flinders University
Tyndall, J. (2008) 'How low can you go? Towards a hierarchy of grey literature'. Presented at Dreaming08: Australian Library and Information Association Biennial Conference, 2-5 September 2008, Alice Springs.