How do I make a business plan for an HR consultancy?

The following search would be a good place to start.

Human Resources Consultancy Business Plan - Google Search (http://www.google.com/search?hl=en&safe=off&q=Human+Resources+Consultancy+Business+Plan)

Then, there is also SCORE | Counselors to America's Small Business | SCORE (http://www.score.org/index.html) and http://www.sba.gov/ which are also excellent resources for finding sample business plans that you could tailor to be your own.