Formatting - Your post need not be a circus. If you are not good with formatting, then stick to a theme that is light and descent in colors and the post layout. If you are good with trying new stuff then use that skill to better express through colors, fonts and layouts. Avoid colors that are dark and fonts that are overtly bright.
Tags: Use of relevant tags is important from the SEO perspective. It helps the search engine track your post based on the tags you use.
Optimize images by mentioning the ALT Text and a short description of the image in your blog post to rank better in Google.