Read first what is the topic all about. Reply what is really in your heart...express it through a good grammar and quality post. Select word which is common and do not used unfamiliar word. Just be your self in answering the topic.
Though this kind of constructing post do not work out these days(it don't really work but sometimes it is). You must be really knowledgeable not only someone that is expressing your heart, that is just like expressing your emotions and not expressing what you really know.
If you want to improve your post quality, you need a massive information in order for you to give opinions to other members about a certain topic. Reading is the best way to improve our posts, Heart is good to be expressed to your loved ones but not in this forum. Members need knowledge, the reason this site called a forum.