Congratulations on your new shop. If it's your own venture, then the sky is the limit. So the harder you try the better your business becomes.
Most of the businesses run by networking and contacts. Selling is a wholesome package, the way you present, the way you highlight the qualities of your products, the cost, the ease and comfort of business and aftersales support. In your case it would mean your image as a seller, the product price ( most competitive), perks cash discounts, free transport, installments etc. Meet the building contractors and their procurement managers, often a small commission would be paid by some for choosing a particular seller. Try and see if you can meet the local builders association, have an office boy who would scout the local area and the surrounding for any individual constructions of homes starting or in progress, then you can meet the owner of the site and request him for some orders. If you can find a contact in the government offices that do infrastructure work, that would too boost your sales.
You can advertise in the local papers and yellow pages. Think of registering yourself as a seller in Indiamart.com or advertising in just dial and another similar search engines with the keywords of construction, cement, steel