The hardest lesson I learned in 2010 was spending a lot of time on 'how the blog' looked, and not focusing on the content. It was my initial mistake as I am an artist, so I like something to look good. By the time I sold a blog, they took the content, but were not interested in the actual blog. I sold it, but afterwards I sat there and realised I spent a lot of time on the 'wrong thing.' The content is what brings people to your blog, so ensure it answers a question.
For example, when I look for cheap mobile phones in the UK, and Google suggests a blog to me, with the 'Ten cheapest Mobiles Phone you can buy for under 100 pounds', I would look at that. Does it make sense?
Just make sure your posts do two major actions: The first action is it should answer the question or paint point of your target audience. The second action on that post is a 'call to action.' Just providing content is not good enough. If people are looking to buy, ensure you are signed up as an affiliate or sell your own products. Build your own email list. Offer an incentive or a freebie, if you are starting an email list. People will always subscribe to your list if it is something they want/need.
If you are starting a blog with the intention of selling it, make sure you take screenshots or have video evidence of your traffic and your monetization techniques. My blog did not make more than $5 per month starting out, however, I explained how they could further monetize it, and how they could scale it. They purchased it, with that intention of scaling it.