Start with a quality article. This means a unique topic or viewpoint on a very specific topic. The information must be valuable to a human reader. At this point in time, it is not possible for any software program to produce content that is engaging. If you start out with a low-quality article, the chances are high that the alternate versions are going to be even worse.
There is also the option to spin capitalized words (assumed to be proper nouns) as well as leave any number of words unchanged, depending on whatever you enter into the "ignore" field, separated by commas. You also have the option to only keep the sentences that were altered a minimum percentage, as indicated by the "Keep Sentences that Changed" option.
Quality readable content is key here. Google, for example, will recognize that people are leaving your site soon after arriving if they perceive that your site or blog is full of junk content. This is called "bounce rate." If your bounce rate is high, then people are quickly leaving your site. But for the sake of your business, to build your online reputation and brand, you want people to visit your site, stay for a while, and then keep revisiting over the long term.