Chamber of Commerce
Get yourself registered with the local Chamber of Commerce and be sure to advertise in their publications. Offering a bit of a special discount to other members can get you more business which is often desirable at the start of any venture. If you have a bi-lingual or multi-lingual Chamber of Commerce in your area, do advertise with them as well.
Make sure that you are in touch with event management firms and offer them your services. Strike a deal that offers flexible terms of service on various volumes of business. These people can promote you big time by bringing more business towards you. Once one firm is attached with you, more likely another company is going to follow suit and you should get more business.
Another good way of promotion is to make your voice heard through local media. You can advertise in the local gazette as well as on the radio channels. Radio is listened to by scores of people and getting an ad on the radio can drive in more business. Getting flyers put in local newspapers is also another good source of promotion and can bring about some good outreach.
Offering Allied Services
Having other services such as a restaurant can both increase the amount of booking the banquet hall will have and also should get you more revenue in general. If you have good food at the restaurant, people will be inclined to holding their functions at your banquet hall expecting similar good work.