Avoid using SMS abbreviations in blog post and at least run the post through a spell-check in MS-Word before publishing. If the bloggers cannot take the time out to write proper English, why would the readers bother reading through that cryptic puzzle?
Spare time to read - Blogging is not just about writing but also about research and reading. Read as much as you can to learn new things and ideas that you can experiment with on your own blog.
Interact with your readers! Reply to their comments, emails and queries. Acknowledging your reader will make them come back to your blog again and again.