If content is king, and I think it is, quality content has to be one’s top priority. Content consists of selection of material, and how it’s presented. Selecting useful and/or entertaining subject matter is a given. Doing one’s best writing is the other part of the equation. You don’t have to be a master literary craftsperson to do a good job. But, you do need to run a spell check, and proofread what you write.
If you, like a blogger I know, need some help with this because you can’t spot mistakes very well, ask someone who is good at it to check your posts periodically and let you know where you need to make corrections. Unfortunately, he doesn’t run it by anyone else, doesn’t do a spell check, and as a result his blog looks like it is written by a third grader who is getting a bad grade in English.
Quality content will draw readers like nothing else will and keep them returning. Doing a good job enhances credibility, shows respect for the reader, and provides other bloggers assurance that if they link to your blog it will enhance theirs.