thought to share some blog commenting techniques, I hope this may helpful for newbies who are commenting on blogs manually !!
1 - make the comment little bit longer and related to the topic, without saying > (thanks for the info, good post, I bookmarked your site and etc)
2 - Comment without common spelling mistake and use good punctuation marks
3 - If they allow to register, do it and then comment. This will gain trust of the admin most of the time
4 - Better to find new blog posts and comment there first
5 - Use a avatar of yours (this will mostly show that u are not a bot)
If you follow these 5 methods, I think mostly your comments will be approved without a problem.