Author of The Consultant with Pink Hair. Sales and marketing advisor to architects, engineers, lawyers, and management consultants in Canada, the US, the Caribbean and Europe.
Focus on your narrow and specific expertise, targeting a very specific type of client and just sell that. In time you may find that you can transfer your very specific functional expertise to other types of clients but do this in a sequential targeted fashion, not a broad approach. Be wary of cross-selling other services in which you are lesser qualified - in most cases it is a fantasy that will waste a lot of your time.
Good luck with your practice.
If you are in Canada there is a program offered by The Canadian Association of Management Consultants (CAMC) and IRAP (Government of Canada agency) that helps small businesses to hire Certified Management Consultants (CMCs). They provide $5,000 in funding (which usually means 30-40 hours of a consultants time as the consultants provide a discounted rate through this program) and there is only a modest ($150?) administration cost to the client. Once you have been approved for the program the CAMC provides you with three consultants to interview and you are free to hire whichever you choose or to request another three choices. The link to the program is here http://www.cmc-canada.ca/provincial_institutes.cfm?Portal_ID=72