Making a good post is all about creativity, you download your creativity, experience and wealth of knowledge to the forum in form of contributions to it's activities.
So when you make a post, preview it, read again and you should ask yourself the level of impact that very post would make on the community whether positive, negative or no impact at all. Truth is that some people don't go through such honest self evaluation before posting and it yields little or no impact.
Making a post only when you have good knowledge for it, have great ideas for discussion and contribution. Knowledge is key, then your experience will decide your post quality.
To make your post is actually helpful for readers and discussion, you must read previous posts too. If answers were asked, issue was solved, you don't need to make your post.
I disagree to say making posts relates to creativity as if you you zero knowledge on the issue is asked for help, and you are trying to make a creative post that is useless and can not help OP or anyone in the discussion. If your creativity misleads OP, readers and relates to fund that can be lost, it's terrible post.
Learn and read before posting will help you increasing your post quality.