A librarian may not have the knowledge of each and every subject pertaining in the library tools. However, he/she must be capable in preparing the documentation on any particular subject. As such he/she should know the highways and byways of the subject for which the documentation is to be prepared. Therefore, he/she should be conversant with the serious step in preparing a documentation. This is a study on the subject documentation and this work . This consists of study of subjects, sources of information and user?s study.