Your blog is an immensely powerful tool that if used effectively can form the basis for extensive and powerful marketing campaigns.
The aim for any marketing is to obviously generate more business. Doing this through a blog is easy enough in theory; in practice though there are a lot of things that can make or break a blog. Not least of these a bit of luck. The most important rule though is consistency. Create and promote consistently and eventually you will begin to find yourself gaining traction.
Your blog should drive traffic to your website. From there you can then direct the traffic along the sales funnel until you convert them into leads or sales.