Someone in Sitepoint ask a question about asking companies to buy advertising space in blog. You definately have to ask people to advertise. It needs work. Even a great product needs promotion. Before selling your ads, you must place advertising space on your blog. Email companies statistic about your blog, price list, and give then screenshot where their ads will be placed.
Your offer must describe your blog’s topic, pageview, and unique visitor statistic. If you can give them statistic about your visitor characteristic, like male or female, your visitor jobs, ages, and location. If the company is familiar with internet marketing, you can also provide them with other statistic like technorati rank, and google PageRank. You should also specify your policy on PageRank, whether you will give backlink or not.
You can offer discount for first time advertisers or discount if they buy 6 months space. You can give them 7 months with a price of 6 months.