Human resource consulting is an $18.4 billion industry that has emerged from management consulting, as clients' needs have become more complex and specialized, widening the gap between HR needs and work force capabilities, and thus accentuating the ability of HR management consulting firms to fill this gap acc to wiki.

For small and medium sized companies who don’t hire a Human Resources manager, employing an HR consulting firm has become vital.
A Human Resource consultant concentrates of compliance issues and following best practices, & assists in employee programs and training and development.
Human Resource consulting needs are certain differ from business to business and city to city.
Services includes legal counseling, global initiatives, investments consulting, and the implementation of HR technologies to facilitate human capital management. The HR consulting industry also employs more actuaries than any other in order to assist in their services. Human Capital including remuneration employee rewards and incentive programs and talent acquisition and management, mergers & Acquisitions, examining fit across culture, job-type, transaction costs, communication, including surveying employee attitudes, satisfaction, engagement, and other employee behaviors

The consulting of human resource revolves around the following core areas like Human Capital; Employee Health Plans and Benefits; Taking care of mergers and acquisitions considering several different variables like culture, cost etc.; Communication across various different departments in an organization.
HR consultancy may help you in the following areas of HR
Performance Enhancement Schemes to help the employees
Assessment & Appraisal schemes to keep the motivation levels high
Competency supported by Salary Systems
Succession & Career Planning to ensure growth of an employee
Job Evaluation, Function resolution & Building up KRAs / KPAs
Organization Diagnostics & Surveys
Quantitative & Qualitative Research
Benchmarking of HR Strategies & Practices will lead to better operation and functioning of the company and its employees.
HR Audit

It can be concluded that a Human Resource management consulting firm empowers an organization to bring in and realize complete potential of its employees; the most valuable resource.