What steps should be taken to be a consultant?

If you are talking about consultancy in Teaching English then I believe proper knowledge of this field is essential.

It is inclusive to knowledge of areas having demand for English teachers, required criteria for teaching English in various countries, specific field in English learning, expected income of an English teacher in different countries and any additional information in this regard for the applicants. 

Developing a fascinating website with maximum data and information is the second step to be a consultant.

Publicity on right spots including online advertisement will put the things on track. 

The last thing to do is quick action to the inquiries of customers and responding in a professional way.

To become a Consultant, I had to finish a Residency in Neurology (5 years, acording the EU regulations). After that the daily work made me improve and get acquainted with the diversity of jobs in a Neurology Service (clinics, A&E, junior doctors education, governance and support to other apecialty wards, medical and surgical.

• In our field as mep engineer should have good experience for materials and good knowledge in design and materials properties 

u need to get so much experience in ur field 

Consultancy services are offered in various fields, like, in education, law, business, psychology, and so on. So, unless you are clear which field attracts you for consultancy services, the question is vague. And since I am a teacher of English, I can answer it only if you seek consultancy in education. 

In which sphere? The question is not clear enough