Stay on topic.
Your comment should be linked to the blog post and not talk about something else.
Be constructive, add value or share your thinking.
A blog can be like a conversation where people talk about what they are thinking about.
Constructive criticism
If you are going to write about how somebody could improve something in their comment, think about how it will sound. Give them ideas, help them out.
Follow our blogging guidelines. http://www.andysclassroom.com/9/category/blogging%20guidelines/1.html
PART 2
Write the comment like a letter (greeting, body, closing, signature).
Use correct spelling, punctuation and spacing.
Read over the comment and editing before submitting.
Compliment the writer in a specific way, asking a question, and/or adding new information to the post.
Write a relevant comment that is related to the post.
Do not reveal personal information in your comment.