Originality - Focus more on the originality of content and on a consistent basis. It is a habit you will need to cultivate.
Don't just type, talk to your audience. Blogging is way big a market on internet and people will like you if you do more than just providing information. Suggest, express, appreciate, criticize and have an opinion to build a relativity to a like minded audience. Make them feel that their visit to your blog matters to you.
For E-commerce bloggers, it is essential to define your audience and take worthy steps to reach out to them. This will be the sole determinant of your marketing plan.