Here are some excellent ideas I found on Kathleen Morris’ blog to help with writing a post:

• Write posts semi-regularly such as every week or two. People might not have a chance to read posts that are published too close together. Readers might forget about your blog if you leave too long a gap between posts.
• Write about something that you are interested in but also something that will interest others. 
• Reply to all/most of your commenters. Readers will be encouraged to comment again if their comment is acknowledged or if they engaged in a conversation.
• Don’t overdo glitter text and keep fonts consistent and easy to read. Yellows and fluro colours are generally very hard to read.
• If you want to use images, use creative commons images, screenshots or your own photos/artwork.
• Make posts easy to read. Left aligning text, using paragraphs, subheadings and/or dot points all helps the reader take in your post more easily.
• End posts with questions to provide readers with commenting prompts. Asking questions that a variety of readers could answer is a skill that will help you to develop as a blogger.
• Proofread and check your facts before publishing. VERY important!