describe how organaization obtains information on employee skills needed to do the jobs?

Answer 1

Well, one easy and free way to see what organizations are looking for in candidates for specific postions is to look up those job titles in any of the major job search sites, like hotjobs.com or monster.com. You can review the postings to see the job descriptions and skills required by specific companies to perform just about any job.

Answer 2

This is tricky, because there are the legal steps that companies should follow, and then there are the actual ways that companies do this.

Usually, a job analysis is performed and then a job description is written. Click here for more job analysis info: http://en.wikipedia.org/wiki/Job_analysis

Maybe I am reading to much into this question, but if you are wondering how your employers are getting away with making you do things that are "not in your job description", the answer is: More and more employers are making their job descriptions vague to allow themselves room to add tasks to your "normal" workload without creating too many legal hassles.