Hi,
I am running an placement consultancy how to develop my business .how can we get clients and convince them recruitng for there companies supplying manpower to them.

Personal contact is best. I would suggest going to the places where there are people for whom you would like to do the work, speak with their human resource person, or whoever hires people, and offer your services as well as have something printed up about your services that you could leave with them. Your going to need to sell what you can do for them to them.

Hopefully, others will come along to offer their suggestions also.

Like Clough said, it is all about selling. You need to show them benefits.